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|
/*-
* Copyright (c) 2014-2015 MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
#include "wt_internal.h"
struct __wt_stuff; typedef struct __wt_stuff WT_STUFF;
struct __wt_track; typedef struct __wt_track WT_TRACK;
struct __wt_track_shared; typedef struct __wt_track_shared WT_TRACK_SHARED;
/*
* There's a bunch of stuff we pass around during salvage, group it together
* to make the code prettier.
*/
struct __wt_stuff {
WT_SESSION_IMPL *session; /* Salvage session */
WT_TRACK **pages; /* Pages */
uint32_t pages_next; /* Next empty slot */
size_t pages_allocated; /* Bytes allocated */
WT_TRACK **ovfl; /* Overflow pages */
uint32_t ovfl_next; /* Next empty slot */
size_t ovfl_allocated; /* Bytes allocated */
WT_REF root_ref; /* Created root page */
uint8_t page_type; /* Page type */
/* If need to free blocks backing merged page ranges. */
int merge_free;
WT_ITEM *tmp1; /* Verbose print buffer */
WT_ITEM *tmp2; /* Verbose print buffer */
uint64_t fcnt; /* Progress counter */
};
/*
* WT_TRACK_SHARED --
* Information shared between pages being merged.
*/
struct __wt_track_shared {
uint32_t ref; /* Reference count */
/*
* Physical information about the file block.
*/
WT_ADDR addr; /* Page address */
uint32_t size; /* Page size */
uint64_t gen; /* Page generation */
/*
* Pages that reference overflow pages contain a list of the overflow
* pages they reference. We start out with a list of addresses, and
* convert to overflow array slots during the reconciliation of page
* references to overflow records.
*/
WT_ADDR *ovfl_addr; /* Overflow pages by address */
uint32_t *ovfl_slot; /* Overflow pages by slot */
uint32_t ovfl_cnt; /* Overflow reference count */
};
/*
* WT_TRACK --
* Structure to track chunks, one per chunk; we start out with a chunk per
* page (either leaf or overflow), but when we find overlapping key ranges, we
* split the leaf page chunks up, one chunk for each unique key range.
*/
struct __wt_track {
#define trk_addr shared->addr.addr
#define trk_addr_size shared->addr.size
#define trk_gen shared->gen
#define trk_ovfl_addr shared->ovfl_addr
#define trk_ovfl_cnt shared->ovfl_cnt
#define trk_ovfl_slot shared->ovfl_slot
#define trk_size shared->size
WT_TRACK_SHARED *shared; /* Shared information */
WT_STUFF *ss; /* Enclosing stuff */
union {
struct {
#undef row_start
#define row_start u.row._row_start
WT_ITEM _row_start; /* Row-store start range */
#undef row_stop
#define row_stop u.row._row_stop
WT_ITEM _row_stop; /* Row-store stop range */
} row;
struct {
#undef col_start
#define col_start u.col._col_start
uint64_t _col_start; /* Col-store start range */
#undef col_stop
#define col_stop u.col._col_stop
uint64_t _col_stop; /* Col-store stop range */
#undef col_missing
#define col_missing u.col._col_missing
uint64_t _col_missing; /* Col-store missing range */
} col;
} u;
#define WT_TRACK_CHECK_START 0x01 /* Row: initial key updated */
#define WT_TRACK_CHECK_STOP 0x02 /* Row: last key updated */
#define WT_TRACK_MERGE 0x04 /* Page requires merging */
#define WT_TRACK_OVFL_REFD 0x08 /* Overflow page referenced */
u_int flags;
};
static int __slvg_cleanup(WT_SESSION_IMPL *, WT_STUFF *);
static int __slvg_col_build_internal(WT_SESSION_IMPL *, uint32_t, WT_STUFF *);
static int __slvg_col_build_leaf(WT_SESSION_IMPL *, WT_TRACK *, WT_REF *);
static int __slvg_col_ovfl(
WT_SESSION_IMPL *, WT_TRACK *, WT_PAGE *, uint64_t, uint64_t);
static int __slvg_col_range(WT_SESSION_IMPL *, WT_STUFF *);
static int __slvg_col_range_missing(WT_SESSION_IMPL *, WT_STUFF *);
static int __slvg_col_range_overlap(
WT_SESSION_IMPL *, uint32_t, uint32_t, WT_STUFF *);
static void __slvg_col_trk_update_start(uint32_t, WT_STUFF *);
static int __slvg_merge_block_free(WT_SESSION_IMPL *, WT_STUFF *);
static int __slvg_ovfl_compare(const void *, const void *);
static int __slvg_ovfl_discard(WT_SESSION_IMPL *, WT_STUFF *);
static int __slvg_ovfl_reconcile(WT_SESSION_IMPL *, WT_STUFF *);
static int __slvg_ovfl_ref(WT_SESSION_IMPL *, WT_TRACK *, int);
static int __slvg_ovfl_ref_all(WT_SESSION_IMPL *, WT_TRACK *);
static int __slvg_read(WT_SESSION_IMPL *, WT_STUFF *);
static int __slvg_row_build_internal(WT_SESSION_IMPL *, uint32_t, WT_STUFF *);
static int __slvg_row_build_leaf(
WT_SESSION_IMPL *, WT_TRACK *, WT_REF *, WT_STUFF *);
static int __slvg_row_ovfl(
WT_SESSION_IMPL *, WT_TRACK *, WT_PAGE *, uint32_t, uint32_t);
static int __slvg_row_range(WT_SESSION_IMPL *, WT_STUFF *);
static int __slvg_row_range_overlap(
WT_SESSION_IMPL *, uint32_t, uint32_t, WT_STUFF *);
static int __slvg_row_trk_update_start(
WT_SESSION_IMPL *, WT_ITEM *, uint32_t, WT_STUFF *);
static int __slvg_trk_compare_addr(const void *, const void *);
static int __slvg_trk_compare_gen(const void *, const void *);
static int __slvg_trk_compare_key(const void *, const void *);
static int __slvg_trk_free(WT_SESSION_IMPL *, WT_TRACK **, int);
static void __slvg_trk_free_addr(WT_SESSION_IMPL *, WT_TRACK *);
static int __slvg_trk_init(WT_SESSION_IMPL *, uint8_t *,
size_t, uint32_t, uint64_t, WT_STUFF *, WT_TRACK **);
static int __slvg_trk_leaf(WT_SESSION_IMPL *,
const WT_PAGE_HEADER *, uint8_t *, size_t, WT_STUFF *);
static int __slvg_trk_leaf_ovfl(
WT_SESSION_IMPL *, const WT_PAGE_HEADER *, WT_TRACK *);
static int __slvg_trk_ovfl(WT_SESSION_IMPL *,
const WT_PAGE_HEADER *, uint8_t *, size_t, WT_STUFF *);
static int __slvg_trk_split(WT_SESSION_IMPL *, WT_TRACK *, WT_TRACK **);
/*
* __wt_bt_salvage --
* Salvage a Btree.
*/
int
__wt_bt_salvage(WT_SESSION_IMPL *session, WT_CKPT *ckptbase, const char *cfg[])
{
WT_BM *bm;
WT_BTREE *btree;
WT_DECL_RET;
WT_STUFF *ss, stuff;
uint32_t i, leaf_cnt;
WT_UNUSED(cfg);
btree = S2BT(session);
bm = btree->bm;
WT_CLEAR(stuff);
ss = &stuff;
ss->session = session;
ss->page_type = WT_PAGE_INVALID;
/* Allocate temporary buffers. */
WT_ERR(__wt_scr_alloc(session, 0, &ss->tmp1));
WT_ERR(__wt_scr_alloc(session, 0, &ss->tmp2));
/*
* Step 1:
* Inform the underlying block manager that we're salvaging the file.
*/
WT_ERR(bm->salvage_start(bm, session));
/*
* Step 2:
* Read the file and build in-memory structures that reference any leaf
* or overflow page. Any pages other than leaf or overflow pages are
* added to the free list.
*
* Turn off read checksum and verification error messages while we're
* reading the file, we expect to see corrupted blocks.
*/
F_SET(session, WT_SESSION_SALVAGE_CORRUPT_OK);
ret = __slvg_read(session, ss);
F_CLR(session, WT_SESSION_SALVAGE_CORRUPT_OK);
WT_ERR(ret);
/*
* Step 3:
* Discard any page referencing a non-existent overflow page. We do
* this before checking overlapping key ranges on the grounds that a
* bad key range we can use is better than a terrific key range that
* references pages we don't have. On the other hand, we subsequently
* discard key ranges where there are better overlapping ranges, and
* it would be better if we let the availability of an overflow value
* inform our choices as to the key ranges we select, ideally on a
* per-key basis.
*
* A complicating problem is found in variable-length column-store
* objects, where we potentially split key ranges within RLE units.
* For example, if there's a page with rows 15-20 and we later find
* row 17 with a larger LSN, the range splits into 3 chunks, 15-16,
* 17, and 18-20. If rows 15-20 were originally a single value (an
* RLE of 6), and that record is an overflow record, we end up with
* two chunks, both of which want to reference the same overflow value.
*
* Instead of the approach just described, we're first discarding any
* pages referencing non-existent overflow pages, then we're reviewing
* our key ranges and discarding any that overlap. We're doing it that
* way for a few reasons: absent corruption, missing overflow items are
* strong arguments the page was replaced (on the other hand, some kind
* of file corruption is probably why we're here); it's a significant
* amount of additional complexity to simultaneously juggle overlapping
* ranges and missing overflow items; finally, real-world applications
* usually don't have a lot of overflow items, as WiredTiger supports
* very large page sizes, overflow items shouldn't be common.
*
* Step 4:
* Add unreferenced overflow page blocks to the free list so they are
* reused immediately.
*/
WT_ERR(__slvg_ovfl_reconcile(session, ss));
WT_ERR(__slvg_ovfl_discard(session, ss));
/*
* Step 5:
* Walk the list of pages looking for overlapping ranges to resolve.
* If we find a range that needs to be resolved, set a global flag
* and a per WT_TRACK flag on the pages requiring modification.
*
* This requires sorting the page list by key, and secondarily by LSN.
*
* !!!
* It's vanishingly unlikely and probably impossible for fixed-length
* column-store files to have overlapping key ranges. It's possible
* for an entire key range to go missing (if a page is corrupted and
* lost), but because pages can't split, it shouldn't be possible to
* find pages where the key ranges overlap. That said, we check for
* it and clean up after it in reconciliation because it doesn't cost
* much and future column-store formats or operations might allow for
* fixed-length format ranges to overlap during salvage, and I don't
* want to have to retrofit the code later.
*/
qsort(ss->pages,
(size_t)ss->pages_next, sizeof(WT_TRACK *), __slvg_trk_compare_key);
if (ss->page_type == WT_PAGE_ROW_LEAF)
WT_ERR(__slvg_row_range(session, ss));
else
WT_ERR(__slvg_col_range(session, ss));
/*
* Step 6:
* We may have lost key ranges in column-store databases, that is, some
* part of the record number space is gone. Look for missing ranges.
*/
switch (ss->page_type) {
case WT_PAGE_COL_FIX:
case WT_PAGE_COL_VAR:
WT_ERR(__slvg_col_range_missing(session, ss));
break;
case WT_PAGE_ROW_LEAF:
break;
}
/*
* Step 7:
* Build an internal page that references all of the leaf pages,
* and write it, as well as any merged pages, to the file.
*
* Count how many leaf pages we have (we could track this during the
* array shuffling/splitting, but that's a lot harder).
*/
for (leaf_cnt = i = 0; i < ss->pages_next; ++i)
if (ss->pages[i] != NULL)
++leaf_cnt;
if (leaf_cnt != 0)
switch (ss->page_type) {
case WT_PAGE_COL_FIX:
case WT_PAGE_COL_VAR:
WT_WITH_PAGE_INDEX(session,
ret = __slvg_col_build_internal(
session, leaf_cnt, ss));
WT_ERR(ret);
break;
case WT_PAGE_ROW_LEAF:
WT_WITH_PAGE_INDEX(session,
ret = __slvg_row_build_internal(
session, leaf_cnt, ss));
WT_ERR(ret);
break;
}
/*
* Step 8:
* If we had to merge key ranges, we have to do a final pass through
* the leaf page array and discard file pages used during key merges.
* We can't do it earlier: if we free'd the leaf pages we're merging as
* we merged them, the write of subsequent leaf pages or the internal
* page might allocate those free'd file blocks, and if the salvage run
* subsequently fails, we'd have overwritten pages used to construct the
* final key range. In other words, if the salvage run fails, we don't
* want to overwrite data the next salvage run might need.
*/
if (ss->merge_free)
WT_ERR(__slvg_merge_block_free(session, ss));
/*
* Step 9:
* Evict the newly created root page, creating a checkpoint.
*/
if (ss->root_ref.page != NULL) {
btree->ckpt = ckptbase;
ret = __wt_evict(session, &ss->root_ref, 1);
ss->root_ref.page = NULL;
btree->ckpt = NULL;
}
/*
* Step 10:
* Inform the underlying block manager that we're done.
*/
err: WT_TRET(bm->salvage_end(bm, session));
/* Discard any root page we created. */
if (ss->root_ref.page != NULL)
__wt_ref_out(session, &ss->root_ref);
/* Discard the leaf and overflow page memory. */
WT_TRET(__slvg_cleanup(session, ss));
/* Discard temporary buffers. */
__wt_scr_free(session, &ss->tmp1);
__wt_scr_free(session, &ss->tmp2);
/* Wrap up reporting. */
WT_TRET(__wt_progress(session, NULL, ss->fcnt));
return (ret);
}
/*
* __slvg_read --
* Read the file and build a table of the pages we can use.
*/
static int
__slvg_read(WT_SESSION_IMPL *session, WT_STUFF *ss)
{
WT_BM *bm;
WT_DECL_ITEM(as);
WT_DECL_ITEM(buf);
WT_DECL_RET;
const WT_PAGE_HEADER *dsk;
size_t addr_size;
uint8_t addr[WT_BTREE_MAX_ADDR_COOKIE];
int eof, valid;
bm = S2BT(session)->bm;
WT_ERR(__wt_scr_alloc(session, 0, &as));
WT_ERR(__wt_scr_alloc(session, 0, &buf));
for (;;) {
/* Get the next block address from the block manager. */
WT_ERR(bm->salvage_next(bm, session, addr, &addr_size, &eof));
if (eof)
break;
/* Report progress every 10 chunks. */
if (++ss->fcnt % 10 == 0)
WT_ERR(__wt_progress(session, NULL, ss->fcnt));
/*
* Read (and potentially decompress) the block; the underlying
* block manager might return only good blocks if checksums are
* configured, or both good and bad blocks if we're relying on
* compression.
*
* Report the block's status to the block manager.
*/
if ((ret = __wt_bt_read(session, buf, addr, addr_size)) == 0)
valid = 1;
else {
valid = 0;
if (ret == WT_ERROR)
ret = 0;
WT_ERR(ret);
}
WT_ERR(bm->salvage_valid(bm, session, addr, addr_size, valid));
if (!valid)
continue;
/* Create a printable version of the address. */
WT_ERR(bm->addr_string(bm, session, as, addr, addr_size));
/*
* Make sure it's an expected page type for the file.
*
* We only care about leaf and overflow pages from here on out;
* discard all of the others. We put them on the free list now,
* because we might as well overwrite them, we want the file to
* grow as little as possible, or shrink, and future salvage
* calls don't need them either.
*/
dsk = buf->data;
switch (dsk->type) {
case WT_PAGE_BLOCK_MANAGER:
case WT_PAGE_COL_INT:
case WT_PAGE_ROW_INT:
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s page ignored %s",
__wt_page_type_string(dsk->type),
(const char *)as->data));
WT_ERR(bm->free(bm, session, addr, addr_size));
continue;
}
/*
* Verify the page. It's unlikely a page could have a valid
* checksum and still be broken, but paranoia is healthy in
* salvage. Regardless, verify does return failure because
* it detects failures we'd expect to see in a corrupted file,
* like overflow references past the end of the file or
* overflow references to non-existent pages, might as well
* discard these pages now.
*/
if (__wt_verify_dsk(session, as->data, buf) != 0) {
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s page failed verify %s",
__wt_page_type_string(dsk->type),
(const char *)as->data));
WT_ERR(bm->free(bm, session, addr, addr_size));
continue;
}
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"tracking %s page, generation %" PRIu64 " %s",
__wt_page_type_string(dsk->type), dsk->write_gen,
(const char *)as->data));
switch (dsk->type) {
case WT_PAGE_COL_FIX:
case WT_PAGE_COL_VAR:
case WT_PAGE_ROW_LEAF:
if (ss->page_type == WT_PAGE_INVALID)
ss->page_type = dsk->type;
if (ss->page_type != dsk->type)
WT_ERR_MSG(session, WT_ERROR,
"file contains multiple file formats (both "
"%s and %s), and cannot be salvaged",
__wt_page_type_string(ss->page_type),
__wt_page_type_string(dsk->type));
WT_ERR(__slvg_trk_leaf(
session, dsk, addr, addr_size, ss));
break;
case WT_PAGE_OVFL:
WT_ERR(__slvg_trk_ovfl(
session, dsk, addr, addr_size, ss));
break;
}
}
err: __wt_scr_free(session, &as);
__wt_scr_free(session, &buf);
return (ret);
}
/*
* __slvg_trk_init --
* Initialize tracking information for a page.
*/
static int
__slvg_trk_init(WT_SESSION_IMPL *session,
uint8_t *addr, size_t addr_size,
uint32_t size, uint64_t gen, WT_STUFF *ss, WT_TRACK **retp)
{
WT_DECL_RET;
WT_TRACK *trk;
WT_RET(__wt_calloc_one(session, &trk));
WT_ERR(__wt_calloc_one(session, &trk->shared));
trk->shared->ref = 1;
trk->ss = ss;
WT_ERR(__wt_strndup(session, addr, addr_size, &trk->trk_addr));
trk->trk_addr_size = (uint8_t)addr_size;
trk->trk_size = size;
trk->trk_gen = gen;
*retp = trk;
return (0);
err: __wt_free(session, trk->trk_addr);
__wt_free(session, trk->shared);
__wt_free(session, trk);
return (ret);
}
/*
* __slvg_trk_split --
* Split a tracked chunk.
*/
static int
__slvg_trk_split(WT_SESSION_IMPL *session, WT_TRACK *orig, WT_TRACK **newp)
{
WT_TRACK *trk;
WT_RET(__wt_calloc_one(session, &trk));
trk->shared = orig->shared;
trk->ss = orig->ss;
++orig->shared->ref;
*newp = trk;
return (0);
}
/*
* __slvg_trk_leaf --
* Track a leaf page.
*/
static int
__slvg_trk_leaf(WT_SESSION_IMPL *session,
const WT_PAGE_HEADER *dsk, uint8_t *addr, size_t addr_size, WT_STUFF *ss)
{
WT_BTREE *btree;
WT_CELL *cell;
WT_CELL_UNPACK *unpack, _unpack;
WT_DECL_RET;
WT_PAGE *page;
WT_TRACK *trk;
uint64_t stop_recno;
uint32_t i;
btree = S2BT(session);
unpack = &_unpack;
page = NULL;
trk = NULL;
/* Re-allocate the array of pages, as necessary. */
WT_RET(__wt_realloc_def(
session, &ss->pages_allocated, ss->pages_next + 1, &ss->pages));
/* Allocate a WT_TRACK entry for this new page and fill it in. */
WT_RET(__slvg_trk_init(
session, addr, addr_size, dsk->mem_size, dsk->write_gen, ss, &trk));
switch (dsk->type) {
case WT_PAGE_COL_FIX:
/*
* Column-store fixed-sized format: start and stop keys can be
* taken from the block's header, and doesn't contain overflow
* items.
*/
trk->col_start = dsk->recno;
trk->col_stop = dsk->recno + (dsk->u.entries - 1);
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s records %" PRIu64 "-%" PRIu64,
__wt_addr_string(
session, trk->trk_addr, trk->trk_addr_size, ss->tmp1),
trk->col_start, trk->col_stop));
break;
case WT_PAGE_COL_VAR:
/*
* Column-store variable-length format: the start key can be
* taken from the block's header, stop key requires walking
* the page.
*/
stop_recno = dsk->recno;
WT_CELL_FOREACH(btree, dsk, cell, unpack, i) {
__wt_cell_unpack(cell, unpack);
stop_recno += __wt_cell_rle(unpack);
}
trk->col_start = dsk->recno;
trk->col_stop = stop_recno - 1;
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s records %" PRIu64 "-%" PRIu64,
__wt_addr_string(
session, trk->trk_addr, trk->trk_addr_size, ss->tmp1),
trk->col_start, trk->col_stop));
/* Column-store pages can contain overflow items. */
WT_ERR(__slvg_trk_leaf_ovfl(session, dsk, trk));
break;
case WT_PAGE_ROW_LEAF:
/*
* Row-store format: copy the first and last keys on the page.
* Keys are prefix-compressed, the simplest and slowest thing
* to do is instantiate the in-memory page, then instantiate
* and copy the full keys, then free the page. We do this
* on every leaf page, and if you need to speed up the salvage,
* it's probably a great place to start.
*/
WT_ERR(__wt_page_inmem(session, NULL, dsk, 0, &page));
WT_ERR(__wt_row_leaf_key_copy(session,
page, &page->pg_row_d[0], &trk->row_start));
WT_ERR(__wt_row_leaf_key_copy(session, page,
&page->pg_row_d[page->pg_row_entries - 1], &trk->row_stop));
if (WT_VERBOSE_ISSET(session, WT_VERB_SALVAGE)) {
WT_ERR(__wt_buf_set_printable(session, ss->tmp1,
trk->row_start.data, trk->row_start.size));
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s start key %.*s",
__wt_addr_string(session,
trk->trk_addr, trk->trk_addr_size, ss->tmp2),
(int)ss->tmp1->size, (char *)ss->tmp1->data));
WT_ERR(__wt_buf_set_printable(session, ss->tmp1,
trk->row_stop.data, trk->row_stop.size));
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s stop key %.*s",
__wt_addr_string(session,
trk->trk_addr, trk->trk_addr_size, ss->tmp2),
(int)ss->tmp1->size, (char *)ss->tmp1->data));
}
/* Row-store pages can contain overflow items. */
WT_ERR(__slvg_trk_leaf_ovfl(session, dsk, trk));
break;
}
ss->pages[ss->pages_next++] = trk;
if (0) {
err: __wt_free(session, trk);
}
if (page != NULL)
__wt_page_out(session, &page);
return (ret);
}
/*
* __slvg_trk_ovfl --
* Track an overflow page.
*/
static int
__slvg_trk_ovfl(WT_SESSION_IMPL *session,
const WT_PAGE_HEADER *dsk, uint8_t *addr, size_t addr_size, WT_STUFF *ss)
{
WT_TRACK *trk;
/*
* Reallocate the overflow page array as necessary, then save the
* page's location information.
*/
WT_RET(__wt_realloc_def(
session, &ss->ovfl_allocated, ss->ovfl_next + 1, &ss->ovfl));
WT_RET(__slvg_trk_init(
session, addr, addr_size, dsk->mem_size, dsk->write_gen, ss, &trk));
ss->ovfl[ss->ovfl_next++] = trk;
return (0);
}
/*
* __slvg_trk_leaf_ovfl --
* Search a leaf page for overflow items.
*/
static int
__slvg_trk_leaf_ovfl(
WT_SESSION_IMPL *session, const WT_PAGE_HEADER *dsk, WT_TRACK *trk)
{
WT_BTREE *btree;
WT_CELL *cell;
WT_CELL_UNPACK *unpack, _unpack;
uint32_t i, ovfl_cnt;
btree = S2BT(session);
unpack = &_unpack;
/*
* Two passes: count the overflow items, then copy them into an
* allocated array.
*/
ovfl_cnt = 0;
WT_CELL_FOREACH(btree, dsk, cell, unpack, i) {
__wt_cell_unpack(cell, unpack);
if (unpack->ovfl)
++ovfl_cnt;
}
if (ovfl_cnt == 0)
return (0);
/* Allocate room for the array of overflow addresses and fill it in. */
WT_RET(__wt_calloc_def(session, ovfl_cnt, &trk->trk_ovfl_addr));
trk->trk_ovfl_cnt = ovfl_cnt;
ovfl_cnt = 0;
WT_CELL_FOREACH(btree, dsk, cell, unpack, i) {
__wt_cell_unpack(cell, unpack);
if (unpack->ovfl) {
WT_RET(__wt_strndup(session, unpack->data,
unpack->size, &trk->trk_ovfl_addr[ovfl_cnt].addr));
trk->trk_ovfl_addr[ovfl_cnt].size =
(uint8_t)unpack->size;
WT_RET(__wt_verbose(session, WT_VERB_SALVAGE,
"%s overflow reference %s",
__wt_addr_string(session,
trk->trk_addr, trk->trk_addr_size, trk->ss->tmp1),
__wt_addr_string(session,
unpack->data, unpack->size, trk->ss->tmp2)));
if (++ovfl_cnt == trk->trk_ovfl_cnt)
break;
}
}
return (0);
}
/*
* __slvg_col_range --
* Figure out the leaf pages we need and free the leaf pages we don't.
*
* When pages split, the key range is split across multiple pages. If not all
* of the old versions of the page are overwritten, or not all of the new pages
* are written, or some of the pages are corrupted, salvage will read different
* pages with overlapping key ranges, at different LSNs.
*
* We salvage all of the key ranges we find, at the latest LSN value: this means
* we may resurrect pages of deleted items, as page deletion doesn't write leaf
* pages and salvage will read and instantiate the contents of an old version of
* the deleted page.
*
* The leaf page array is sorted in key order, and secondarily on LSN: what this
* means is that for each new key range, the first page we find is the best page
* for that key. The process is to walk forward from each page until we reach
* a page with a starting key after the current page's stopping key.
*
* For each of page, check to see if they overlap the current page's key range.
* If they do, resolve the overlap. Because WiredTiger rarely splits pages,
* overlap resolution usually means discarding a page because the key ranges
* are the same, and one of the pages is simply an old version of the other.
*
* However, it's possible more complex resolution is necessary. For example,
* here's an improbably complex list of page ranges and LSNs:
*
* Page Range LSN
* 30 A-G 3
* 31 C-D 4
* 32 B-C 5
* 33 C-F 6
* 34 C-D 7
* 35 F-M 8
* 36 H-O 9
*
* We walk forward from each page reviewing all other pages in the array that
* overlap the range. For each overlap, the current or the overlapping
* page is updated so the page with the most recent information for any range
* "owns" that range. Here's an example for page 30.
*
* Review page 31: because page 31 has the range C-D and a higher LSN than page
* 30, page 30 would "split" into two ranges, A-C and E-G, conceding the C-D
* range to page 31. The new track element would be inserted into array with
* the following result:
*
* Page Range LSN
* 30 A-C 3 << Changed WT_TRACK element
* 31 C-D 4
* 32 B-C 5
* 33 C-F 6
* 34 C-D 7
* 30 E-G 3 << New WT_TRACK element
* 35 F-M 8
* 36 H-O 9
*
* Continue the review of the first element, using its new values.
*
* Review page 32: because page 31 has the range B-C and a higher LSN than page
* 30, page 30's A-C range would be truncated, conceding the B-C range to page
* 32.
* 30 A-B 3
* E-G 3
* 31 C-D 4
* 32 B-C 5
* 33 C-F 6
* 34 C-D 7
*
* Review page 33: because page 33 has a starting key (C) past page 30's ending
* key (B), we stop evaluating page 30's A-B range, as there can be no further
* overlaps.
*
* This process is repeated for each page in the array.
*
* When page 33 is processed, we'd discover that page 33's C-F range overlaps
* page 30's E-G range, and page 30's E-G range would be updated, conceding the
* E-F range to page 33.
*
* This is not computationally expensive because we don't walk far forward in
* the leaf array because it's sorted by starting key, and because WiredTiger
* splits are rare, the chance of finding the kind of range overlap requiring
* re-sorting the array is small.
*/
static int
__slvg_col_range(WT_SESSION_IMPL *session, WT_STUFF *ss)
{
WT_TRACK *jtrk;
uint32_t i, j;
/*
* DO NOT MODIFY THIS CODE WITHOUT REVIEWING THE CORRESPONDING ROW- OR
* COLUMN-STORE CODE: THEY ARE IDENTICAL OTHER THAN THE PAGES THAT ARE
* BEING HANDLED.
*
* Walk the page array looking for overlapping key ranges, adjusting
* the ranges based on the LSN until there are no overlaps.
*
* DO NOT USE POINTERS INTO THE ARRAY: THE ARRAY IS RE-SORTED IN PLACE
* AS ENTRIES ARE SPLIT, SO ARRAY REFERENCES MUST ALWAYS BE ARRAY BASE
* PLUS OFFSET.
*/
for (i = 0; i < ss->pages_next; ++i) {
if (ss->pages[i] == NULL)
continue;
/* Check for pages that overlap our page. */
for (j = i + 1; j < ss->pages_next; ++j) {
if (ss->pages[j] == NULL)
continue;
/*
* We're done if this page starts after our stop, no
* subsequent pages can overlap our page.
*/
if (ss->pages[j]->col_start >
ss->pages[i]->col_stop)
break;
/* There's an overlap, fix it up. */
jtrk = ss->pages[j];
WT_RET(__slvg_col_range_overlap(session, i, j, ss));
/*
* If the overlap resolution changed the entry's start
* key, the entry might have moved and the page array
* re-sorted, and pages[j] would reference a different
* page. We don't move forward if that happened, we
* re-process the slot again (by decrementing j before
* the loop's increment).
*/
if (ss->pages[j] != NULL && jtrk != ss->pages[j])
--j;
}
}
return (0);
}
/*
* __slvg_col_range_overlap --
* Two column-store key ranges overlap, deal with it.
*/
static int
__slvg_col_range_overlap(
WT_SESSION_IMPL *session, uint32_t a_slot, uint32_t b_slot, WT_STUFF *ss)
{
WT_TRACK *a_trk, *b_trk, *new;
uint32_t i;
/*
* DO NOT MODIFY THIS CODE WITHOUT REVIEWING THE CORRESPONDING ROW- OR
* COLUMN-STORE CODE: THEY ARE IDENTICAL OTHER THAN THE PAGES THAT ARE
* BEING HANDLED.
*/
a_trk = ss->pages[a_slot];
b_trk = ss->pages[b_slot];
WT_RET(__wt_verbose(session, WT_VERB_SALVAGE,
"%s and %s range overlap",
__wt_addr_string(
session, a_trk->trk_addr, a_trk->trk_addr_size, ss->tmp1),
__wt_addr_string(
session, b_trk->trk_addr, b_trk->trk_addr_size, ss->tmp2)));
/*
* The key ranges of two WT_TRACK pages in the array overlap -- choose
* the ranges we're going to take from each.
*
* We can think of the overlap possibilities as 11 different cases:
*
* AAAAAAAAAAAAAAAAAA
* #1 BBBBBBBBBBBBBBBBBB pages are the same
* #2 BBBBBBBBBBBBB overlaps the beginning
* #3 BBBBBBBBBBBBBBBB overlaps the end
* #4 BBBBB B is a prefix of A
* #5 BBBBBB B is middle of A
* #6 BBBBBBBBBB B is a suffix of A
*
* and:
*
* BBBBBBBBBBBBBBBBBB
* #7 AAAAAAAAAAAAA same as #3
* #8 AAAAAAAAAAAAAAAA same as #2
* #9 AAAAA A is a prefix of B
* #10 AAAAAA A is middle of B
* #11 AAAAAAAAAA A is a suffix of B
*
* Note the leaf page array was sorted by key and a_trk appears earlier
* in the array than b_trk, so cases #2/8, #10 and #11 are impossible.
*
* Finally, there's one additional complicating factor -- final ranges
* are assigned based on the page's LSN.
*/
/* Case #2/8, #10, #11 */
if (a_trk->col_start > b_trk->col_start)
WT_PANIC_RET(
session, EINVAL, "unexpected merge array sort order");
if (a_trk->col_start == b_trk->col_start) { /* Case #1, #4 and #9 */
/*
* The secondary sort of the leaf page array was the page's LSN,
* in high-to-low order, which means a_trk has a higher LSN, and
* is more desirable, than b_trk. In cases #1 and #4 and #9,
* where the start of the range is the same for the two pages,
* this simplifies things, it guarantees a_trk has a higher LSN
* than b_trk.
*/
if (a_trk->col_stop >= b_trk->col_stop)
/*
* Case #1, #4: a_trk is a superset of b_trk, and a_trk
* is more desirable -- discard b_trk.
*/
goto delete_b;
/*
* Case #9: b_trk is a superset of a_trk, but a_trk is more
* desirable: keep both but delete a_trk's key range from
* b_trk.
*/
b_trk->col_start = a_trk->col_stop + 1;
__slvg_col_trk_update_start(b_slot, ss);
F_SET(b_trk, WT_TRACK_MERGE);
goto merge;
}
if (a_trk->col_stop == b_trk->col_stop) { /* Case #6 */
if (a_trk->trk_gen > b_trk->trk_gen)
/*
* Case #6: a_trk is a superset of b_trk and a_trk is
* more desirable -- discard b_trk.
*/
goto delete_b;
/*
* Case #6: a_trk is a superset of b_trk, but b_trk is more
* desirable: keep both but delete b_trk's key range from a_trk.
*/
a_trk->col_stop = b_trk->col_start - 1;
F_SET(a_trk, WT_TRACK_MERGE);
goto merge;
}
if (a_trk->col_stop < b_trk->col_stop) { /* Case #3/7 */
if (a_trk->trk_gen > b_trk->trk_gen) {
/*
* Case #3/7: a_trk is more desirable, delete a_trk's
* key range from b_trk;
*/
b_trk->col_start = a_trk->col_stop + 1;
__slvg_col_trk_update_start(b_slot, ss);
F_SET(b_trk, WT_TRACK_MERGE);
} else {
/*
* Case #3/7: b_trk is more desirable, delete b_trk's
* key range from a_trk;
*/
a_trk->col_stop = b_trk->col_start - 1;
F_SET(a_trk, WT_TRACK_MERGE);
}
goto merge;
}
/*
* Case #5: a_trk is a superset of b_trk and a_trk is more desirable --
* discard b_trk.
*/
if (a_trk->trk_gen > b_trk->trk_gen) {
delete_b: /*
* After page and overflow reconciliation, one (and only one)
* page can reference an overflow record. But, if we split a
* page into multiple chunks, any of the chunks might own any
* of the backing overflow records, so overflow records won't
* normally be discarded until after the merge phase completes.
* (The merge phase is where the final pages are written, and
* we figure out which overflow records are actually used.)
* If freeing a chunk and there are no other references to the
* underlying shared information, the overflow records must be
* useless, discard them to keep the final file size small.
*/
if (b_trk->shared->ref == 1)
for (i = 0; i < b_trk->trk_ovfl_cnt; ++i)
WT_RET(__slvg_trk_free(session,
&ss->ovfl[b_trk->trk_ovfl_slot[i]], 1));
return (__slvg_trk_free(session, &ss->pages[b_slot], 1));
}
/*
* Case #5: b_trk is more desirable and is a middle chunk of a_trk.
* Split a_trk into two parts, the key range before b_trk and the
* key range after b_trk.
*/
WT_RET(__slvg_trk_split(session, a_trk, &new));
/*
* Second, reallocate the array of pages if necessary, and then insert
* the new element into the array after the existing element (that's
* probably wrong, but we'll fix it up in a second).
*/
WT_RET(__wt_realloc_def(
session, &ss->pages_allocated, ss->pages_next + 1, &ss->pages));
memmove(ss->pages + a_slot + 1, ss->pages + a_slot,
(ss->pages_next - a_slot) * sizeof(*ss->pages));
ss->pages[a_slot + 1] = new;
++ss->pages_next;
/*
* Third, set its start key to be the first key after the stop key of
* the middle chunk (that's b_trk), and its stop key to be the stop key
* of the original chunk, and call __slvg_col_trk_update_start. That
* function will re-sort the WT_TRACK array as necessary to move our
* new entry into the right sorted location.
*/
new->col_start = b_trk->col_stop + 1;
new->col_stop = a_trk->col_stop;
__slvg_col_trk_update_start(a_slot + 1, ss);
/*
* Fourth, set the original WT_TRACK information to reference only
* the initial key space in the page, that is, everything up to the
* starting key of the middle chunk (that's b_trk).
*/
a_trk->col_stop = b_trk->col_start - 1;
F_SET(new, WT_TRACK_MERGE);
F_SET(a_trk, WT_TRACK_MERGE);
merge: WT_RET(__wt_verbose(session, WT_VERB_SALVAGE,
"%s and %s require merge",
__wt_addr_string(
session, a_trk->trk_addr, a_trk->trk_addr_size, ss->tmp1),
__wt_addr_string(
session, b_trk->trk_addr, b_trk->trk_addr_size, ss->tmp2)));
return (0);
}
/*
* __slvg_col_trk_update_start --
* Update a column-store page's start key after an overlap.
*/
static void
__slvg_col_trk_update_start(uint32_t slot, WT_STUFF *ss)
{
WT_TRACK *trk;
uint32_t i;
trk = ss->pages[slot];
/*
* If we deleted an initial piece of the WT_TRACK name space, it may no
* longer be in the right location.
*
* For example, imagine page #1 has the key range 30-50, it split, and
* we wrote page #2 with key range 30-40, and page #3 key range with
* 40-50, where pages #2 and #3 have larger LSNs than page #1. When the
* key ranges were sorted, page #2 came first, then page #1 (because of
* their earlier start keys than page #3), and page #2 came before page
* #1 because of its LSN. When we resolve the overlap between page #2
* and page #1, we truncate the initial key range of page #1, and it now
* sorts after page #3, because it has the same starting key of 40, and
* a lower LSN.
*
* We have already updated b_trk's start key; what we may have to do is
* re-sort some number of elements in the list.
*/
for (i = slot + 1; i < ss->pages_next; ++i) {
if (ss->pages[i] == NULL)
continue;
if (ss->pages[i]->col_start > trk->col_stop)
break;
}
i -= slot;
if (i > 1)
qsort(ss->pages + slot, (size_t)i,
sizeof(WT_TRACK *), __slvg_trk_compare_key);
}
/*
* __slvg_col_range_missing --
* Detect missing ranges from column-store files.
*/
static int
__slvg_col_range_missing(WT_SESSION_IMPL *session, WT_STUFF *ss)
{
WT_TRACK *trk;
uint64_t r;
uint32_t i;
for (i = 0, r = 0; i < ss->pages_next; ++i) {
if ((trk = ss->pages[i]) == NULL)
continue;
if (trk->col_start != r + 1) {
WT_RET(__wt_verbose(session, WT_VERB_SALVAGE,
"%s column-store missing range from %"
PRIu64 " to %" PRIu64 " inclusive",
__wt_addr_string(session,
trk->trk_addr, trk->trk_addr_size, ss->tmp1),
r + 1, trk->col_start - 1));
/*
* We need to instantiate deleted items for the missing
* record range.
*/
trk->col_missing = r + 1;
F_SET(trk, WT_TRACK_MERGE);
}
r = trk->col_stop;
}
return (0);
}
/*
* __slvg_modify_init --
* Initialize a salvage page's modification information.
*/
static int
__slvg_modify_init(WT_SESSION_IMPL *session, WT_PAGE *page)
{
WT_RET(__wt_page_modify_init(session, page));
__wt_page_modify_set(session, page);
return (0);
}
/*
* __slvg_col_build_internal --
* Build a column-store in-memory page that references all of the leaf
* pages we've found.
*/
static int
__slvg_col_build_internal(
WT_SESSION_IMPL *session, uint32_t leaf_cnt, WT_STUFF *ss)
{
WT_ADDR *addr;
WT_DECL_RET;
WT_PAGE *page;
WT_PAGE_INDEX *pindex;
WT_REF *ref, **refp;
WT_TRACK *trk;
uint32_t i;
addr = NULL;
/* Allocate a column-store root (internal) page and fill it in. */
WT_RET(
__wt_page_alloc(session, WT_PAGE_COL_INT, 1, leaf_cnt, 1, &page));
WT_ERR(__slvg_modify_init(session, page));
pindex = WT_INTL_INDEX_COPY(page);
for (refp = pindex->index, i = 0; i < ss->pages_next; ++i) {
if ((trk = ss->pages[i]) == NULL)
continue;
ref = *refp++;
ref->home = page;
ref->page = NULL;
WT_ERR(__wt_calloc_one(session, &addr));
WT_ERR(__wt_strndup(
session, trk->trk_addr, trk->trk_addr_size, &addr->addr));
addr->size = trk->trk_addr_size;
addr->type =
trk->trk_ovfl_cnt == 0 ? WT_ADDR_LEAF_NO : WT_ADDR_LEAF;
ref->addr = addr;
addr = NULL;
ref->key.recno = trk->col_start;
ref->state = WT_REF_DISK;
/*
* If the page's key range is unmodified from when we read it
* (in other words, we didn't merge part of this page with
* another page), we can use the page without change, and the
* only thing we need to do is mark all overflow records the
* page references as in-use.
*
* If we did merge with another page, we have to build a page
* reflecting the updated key range. Note, that requires an
* additional pass to free the merge page's backing blocks.
*/
if (F_ISSET(trk, WT_TRACK_MERGE)) {
ss->merge_free = 1;
WT_ERR(__slvg_col_build_leaf(session, trk, ref));
} else
WT_ERR(__slvg_ovfl_ref_all(session, trk));
++ref;
}
__wt_root_ref_init(&ss->root_ref, page, 1);
if (0) {
err: if (addr != NULL)
__wt_free(session, addr);
__wt_page_out(session, &page);
}
return (ret);
}
/*
* __slvg_col_build_leaf --
* Build a column-store leaf page for a merged page.
*/
static int
__slvg_col_build_leaf(WT_SESSION_IMPL *session, WT_TRACK *trk, WT_REF *ref)
{
WT_COL *save_col_var;
WT_DECL_RET;
WT_PAGE *page;
WT_SALVAGE_COOKIE *cookie, _cookie;
uint64_t skip, take;
uint32_t *entriesp, save_entries;
cookie = &_cookie;
WT_CLEAR(*cookie);
/* Get the original page, including the full in-memory setup. */
WT_RET(__wt_page_in(session, ref, 0));
page = ref->page;
entriesp = page->type == WT_PAGE_COL_VAR ?
&page->pg_var_entries : &page->pg_fix_entries;
save_col_var = page->pg_var_d;
save_entries = *entriesp;
/*
* Calculate the number of K/V entries we are going to skip, and
* the total number of K/V entries we'll take from this page.
*/
cookie->skip = skip = trk->col_start - page->pg_var_recno;
cookie->take = take = (trk->col_stop - trk->col_start) + 1;
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s merge discarding first %" PRIu64 " records, "
"then taking %" PRIu64 " records",
__wt_addr_string(
session, trk->trk_addr, trk->trk_addr_size, trk->ss->tmp1),
skip, take));
/* Set the referenced flag on overflow pages we're using. */
if (page->type == WT_PAGE_COL_VAR && trk->trk_ovfl_cnt != 0)
WT_ERR(__slvg_col_ovfl(session, trk, page, skip, take));
/*
* If we're missing some part of the range, the real start range is in
* trk->col_missing, else, it's in trk->col_start. Update the parent's
* reference as well as the page itself.
*/
if (trk->col_missing == 0)
page->pg_var_recno = trk->col_start;
else {
page->pg_var_recno = trk->col_missing;
cookie->missing = trk->col_start - trk->col_missing;
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s merge inserting %" PRIu64 " missing records",
__wt_addr_string(
session, trk->trk_addr, trk->trk_addr_size, trk->ss->tmp1),
cookie->missing));
}
ref->key.recno = page->pg_var_recno;
/*
* We can't discard the original blocks associated with this page now.
* (The problem is we don't want to overwrite any original information
* until the salvage run succeeds -- if we free the blocks now, the next
* merge page we write might allocate those blocks and overwrite them,
* and should the salvage run eventually fail, the original information
* would have been lost.) Clear the reference addr so eviction doesn't
* free the underlying blocks.
*/
__wt_free(session, ((WT_ADDR *)ref->addr)->addr);
__wt_free(session, ref->addr);
ref->addr = NULL;
/* Write the new version of the leaf page to disk. */
WT_ERR(__slvg_modify_init(session, page));
WT_ERR(__wt_reconcile(session, ref, cookie, WT_SKIP_UPDATE_ERR));
/* Reset the page. */
page->pg_var_d = save_col_var;
*entriesp = save_entries;
ret = __wt_page_release(session, ref, 0);
if (ret == 0)
ret = __wt_evict(session, ref, 1);
if (0) {
err: WT_TRET(__wt_page_release(session, ref, 0));
}
return (ret);
}
/*
* __slvg_col_ovfl_single --
* Find a single overflow record in the merge page's list, and mark it as
* referenced.
*/
static int
__slvg_col_ovfl_single(
WT_SESSION_IMPL *session, WT_TRACK *trk, WT_CELL_UNPACK *unpack)
{
WT_TRACK *ovfl;
uint32_t i;
/*
* Search the list of overflow records for this page -- we should find
* exactly one match, and we mark it as referenced.
*/
for (i = 0; i < trk->trk_ovfl_cnt; ++i) {
ovfl = trk->ss->ovfl[trk->trk_ovfl_slot[i]];
if (unpack->size == ovfl->trk_addr_size &&
memcmp(unpack->data, ovfl->trk_addr, unpack->size) == 0)
return (__slvg_ovfl_ref(session, ovfl, 0));
}
WT_PANIC_RET(session,
EINVAL, "overflow record at column-store page merge not found");
}
/*
* __slvg_col_ovfl --
* Mark overflow items referenced by the merged page.
*/
static int
__slvg_col_ovfl(WT_SESSION_IMPL *session,
WT_TRACK *trk, WT_PAGE *page, uint64_t skip, uint64_t take)
{
WT_CELL_UNPACK unpack;
WT_CELL *cell;
WT_COL *cip;
WT_DECL_RET;
uint64_t recno, start, stop;
uint32_t i;
/*
* Merging a variable-length column-store page, and we took some number
* of records, figure out which (if any) overflow records we used.
*/
recno = page->pg_var_recno;
start = recno + skip;
stop = (recno + skip + take) - 1;
WT_COL_FOREACH(page, cip, i) {
cell = WT_COL_PTR(page, cip);
__wt_cell_unpack(cell, &unpack);
recno += __wt_cell_rle(&unpack);
/*
* I keep getting this calculation wrong, so here's the logic.
* Start is the first record we want, stop is the last record
* we want. The record number has already been incremented one
* past the maximum record number for this page entry, that is,
* it's set to the first record number for the next page entry.
* The test of start should be greater-than (not greater-than-
* or-equal), because of that increment, if the record number
* equals start, we want the next record, not this one. The
* test against stop is greater-than, not greater-than-or-equal
* because stop is the last record wanted, if the record number
* equals stop, we want the next record.
*/
if (recno > start && unpack.type == WT_CELL_VALUE_OVFL) {
ret = __slvg_col_ovfl_single(session, trk, &unpack);
/*
* When handling overlapping ranges on variable-length
* column-store leaf pages, we split ranges without
* considering if we were splitting RLE units. (See
* note at the beginning of this file for explanation
* of the overall process.) If the RLE unit was on-page,
* we can simply write it again. If the RLE unit was an
* overflow value that's already been used by another
* row (from some other page created by a range split),
* there's not much to do, this row can't reference an
* overflow record we don't have: delete the row.
*/
if (ret == EBUSY) {
__wt_cell_type_reset(session,
cell, WT_CELL_VALUE_OVFL, WT_CELL_DEL);
ret = 0;
}
WT_RET(ret);
}
if (recno > stop)
break;
}
return (0);
}
/*
* __slvg_row_range --
* Figure out the leaf pages we need and discard everything else. At the
* same time, tag the overflow pages they reference.
*/
static int
__slvg_row_range(WT_SESSION_IMPL *session, WT_STUFF *ss)
{
WT_TRACK *jtrk;
WT_BTREE *btree;
uint32_t i, j;
int cmp;
btree = S2BT(session);
/*
* DO NOT MODIFY THIS CODE WITHOUT REVIEWING THE CORRESPONDING ROW- OR
* COLUMN-STORE CODE: THEY ARE IDENTICAL OTHER THAN THE PAGES THAT ARE
* BEING HANDLED.
*
* Walk the page array looking for overlapping key ranges, adjusting
* the ranges based on the LSN until there are no overlaps.
*
* DO NOT USE POINTERS INTO THE ARRAY: THE ARRAY IS RE-SORTED IN PLACE
* AS ENTRIES ARE SPLIT, SO ARRAY REFERENCES MUST ALWAYS BE ARRAY BASE
* PLUS OFFSET.
*/
for (i = 0; i < ss->pages_next; ++i) {
if (ss->pages[i] == NULL)
continue;
/* Check for pages that overlap our page. */
for (j = i + 1; j < ss->pages_next; ++j) {
if (ss->pages[j] == NULL)
continue;
/*
* We're done if this page starts after our stop, no
* subsequent pages can overlap our page.
*/
WT_RET(__wt_compare(session, btree->collator,
&ss->pages[j]->row_start, &ss->pages[i]->row_stop,
&cmp));
if (cmp > 0)
break;
/* There's an overlap, fix it up. */
jtrk = ss->pages[j];
WT_RET(__slvg_row_range_overlap(session, i, j, ss));
/*
* If the overlap resolution changed the entry's start
* key, the entry might have moved and the page array
* re-sorted, and pages[j] would reference a different
* page. We don't move forward if that happened, we
* re-process the slot again (by decrementing j before
* the loop's increment).
*/
if (ss->pages[j] != NULL && jtrk != ss->pages[j])
--j;
}
}
return (0);
}
/*
* __slvg_row_range_overlap --
* Two row-store key ranges overlap, deal with it.
*/
static int
__slvg_row_range_overlap(
WT_SESSION_IMPL *session, uint32_t a_slot, uint32_t b_slot, WT_STUFF *ss)
{
WT_BTREE *btree;
WT_TRACK *a_trk, *b_trk, *new;
uint32_t i;
int start_cmp, stop_cmp;
/*
* DO NOT MODIFY THIS CODE WITHOUT REVIEWING THE CORRESPONDING ROW- OR
* COLUMN-STORE CODE: THEY ARE IDENTICAL OTHER THAN THE PAGES THAT ARE
* BEING HANDLED.
*/
btree = S2BT(session);
a_trk = ss->pages[a_slot];
b_trk = ss->pages[b_slot];
WT_RET(__wt_verbose(session, WT_VERB_SALVAGE,
"%s and %s range overlap",
__wt_addr_string(
session, a_trk->trk_addr, a_trk->trk_addr_size, ss->tmp1),
__wt_addr_string(
session, b_trk->trk_addr, b_trk->trk_addr_size, ss->tmp2)));
/*
* The key ranges of two WT_TRACK pages in the array overlap -- choose
* the ranges we're going to take from each.
*
* We can think of the overlap possibilities as 11 different cases:
*
* AAAAAAAAAAAAAAAAAA
* #1 BBBBBBBBBBBBBBBBBB pages are the same
* #2 BBBBBBBBBBBBB overlaps the beginning
* #3 BBBBBBBBBBBBBBBB overlaps the end
* #4 BBBBB B is a prefix of A
* #5 BBBBBB B is middle of A
* #6 BBBBBBBBBB B is a suffix of A
*
* and:
*
* BBBBBBBBBBBBBBBBBB
* #7 AAAAAAAAAAAAA same as #3
* #8 AAAAAAAAAAAAAAAA same as #2
* #9 AAAAA A is a prefix of B
* #10 AAAAAA A is middle of B
* #11 AAAAAAAAAA A is a suffix of B
*
* Note the leaf page array was sorted by key and a_trk appears earlier
* in the array than b_trk, so cases #2/8, #10 and #11 are impossible.
*
* Finally, there's one additional complicating factor -- final ranges
* are assigned based on the page's LSN.
*/
#define A_TRK_START (&a_trk->row_start)
#define A_TRK_STOP (&a_trk->row_stop)
#define B_TRK_START (&b_trk->row_start)
#define B_TRK_STOP (&b_trk->row_stop)
#define SLOT_START(i) (&ss->pages[i]->row_start)
#define __slvg_key_copy(session, dst, src) \
__wt_buf_set(session, dst, (src)->data, (src)->size)
WT_RET(__wt_compare(
session, btree->collator, A_TRK_START, B_TRK_START, &start_cmp));
WT_RET(__wt_compare(
session, btree->collator, A_TRK_STOP, B_TRK_STOP, &stop_cmp));
if (start_cmp > 0) /* Case #2/8, #10, #11 */
WT_PANIC_RET(
session, EINVAL, "unexpected merge array sort order");
if (start_cmp == 0) { /* Case #1, #4, #9 */
/*
* The secondary sort of the leaf page array was the page's LSN,
* in high-to-low order, which means a_trk has a higher LSN, and
* is more desirable, than b_trk. In cases #1 and #4 and #9,
* where the start of the range is the same for the two pages,
* this simplifies things, it guarantees a_trk has a higher LSN
* than b_trk.
*/
if (stop_cmp >= 0)
/*
* Case #1, #4: a_trk is a superset of b_trk, and a_trk
* is more desirable -- discard b_trk.
*/
goto delete_b;
/*
* Case #9: b_trk is a superset of a_trk, but a_trk is more
* desirable: keep both but delete a_trk's key range from
* b_trk.
*/
WT_RET(__slvg_row_trk_update_start(
session, A_TRK_STOP, b_slot, ss));
F_SET(b_trk, WT_TRACK_CHECK_START | WT_TRACK_MERGE);
goto merge;
}
if (stop_cmp == 0) { /* Case #6 */
if (a_trk->trk_gen > b_trk->trk_gen)
/*
* Case #6: a_trk is a superset of b_trk and a_trk is
* more desirable -- discard b_trk.
*/
goto delete_b;
/*
* Case #6: a_trk is a superset of b_trk, but b_trk is more
* desirable: keep both but delete b_trk's key range from a_trk.
*/
WT_RET(__slvg_key_copy(session, A_TRK_STOP, B_TRK_START));
F_SET(a_trk, WT_TRACK_CHECK_STOP | WT_TRACK_MERGE);
goto merge;
}
if (stop_cmp < 0) { /* Case #3/7 */
if (a_trk->trk_gen > b_trk->trk_gen) {
/*
* Case #3/7: a_trk is more desirable, delete a_trk's
* key range from b_trk;
*/
WT_RET(__slvg_row_trk_update_start(
session, A_TRK_STOP, b_slot, ss));
F_SET(b_trk, WT_TRACK_CHECK_START | WT_TRACK_MERGE);
} else {
/*
* Case #3/7: b_trk is more desirable, delete b_trk's
* key range from a_trk;
*/
WT_RET(__slvg_key_copy(
session, A_TRK_STOP, B_TRK_START));
F_SET(a_trk, WT_TRACK_CHECK_STOP | WT_TRACK_MERGE);
}
goto merge;
}
/*
* Case #5: a_trk is a superset of b_trk and a_trk is more desirable --
* discard b_trk.
*/
if (a_trk->trk_gen > b_trk->trk_gen) {
delete_b: /*
* After page and overflow reconciliation, one (and only one)
* page can reference an overflow record. But, if we split a
* page into multiple chunks, any of the chunks might own any
* of the backing overflow records, so overflow records won't
* normally be discarded until after the merge phase completes.
* (The merge phase is where the final pages are written, and
* we figure out which overflow records are actually used.)
* If freeing a chunk and there are no other references to the
* underlying shared information, the overflow records must be
* useless, discard them to keep the final file size small.
*/
if (b_trk->shared->ref == 1)
for (i = 0; i < b_trk->trk_ovfl_cnt; ++i)
WT_RET(__slvg_trk_free(session,
&ss->ovfl[b_trk->trk_ovfl_slot[i]], 1));
return (__slvg_trk_free(session, &ss->pages[b_slot], 1));
}
/*
* Case #5: b_trk is more desirable and is a middle chunk of a_trk.
* Split a_trk into two parts, the key range before b_trk and the
* key range after b_trk.
*/
WT_RET(__slvg_trk_split(session, a_trk, &new));
/*
* Second, reallocate the array of pages if necessary, and then insert
* the new element into the array after the existing element (that's
* probably wrong, but we'll fix it up in a second).
*/
WT_RET(__wt_realloc_def(
session, &ss->pages_allocated, ss->pages_next + 1, &ss->pages));
memmove(ss->pages + a_slot + 1, ss->pages + a_slot,
(ss->pages_next - a_slot) * sizeof(*ss->pages));
ss->pages[a_slot + 1] = new;
++ss->pages_next;
/*
* Third, set its its stop key to be the stop key of the original chunk,
* and call __slvg_row_trk_update_start. That function will both set
* the start key to be the first key after the stop key of the middle
* chunk (that's b_trk), and re-sort the WT_TRACK array as necessary to
* move our new entry into the right sorted location.
*/
WT_RET(__slvg_key_copy(session, &new->row_stop, A_TRK_STOP));
WT_RET(
__slvg_row_trk_update_start(session, B_TRK_STOP, a_slot + 1, ss));
/*
* Fourth, set the original WT_TRACK information to reference only
* the initial key space in the page, that is, everything up to the
* starting key of the middle chunk (that's b_trk).
*/
WT_RET(__slvg_key_copy(session, A_TRK_STOP, B_TRK_START));
F_SET(new, WT_TRACK_CHECK_START);
F_SET(a_trk, WT_TRACK_CHECK_STOP);
F_SET(new, WT_TRACK_MERGE);
F_SET(a_trk, WT_TRACK_MERGE);
merge: WT_RET(__wt_verbose(session, WT_VERB_SALVAGE,
"%s and %s require merge",
__wt_addr_string(
session, a_trk->trk_addr, a_trk->trk_addr_size, ss->tmp1),
__wt_addr_string(
session, b_trk->trk_addr, b_trk->trk_addr_size, ss->tmp2)));
return (0);
}
/*
* __slvg_row_trk_update_start --
* Update a row-store page's start key after an overlap.
*/
static int
__slvg_row_trk_update_start(
WT_SESSION_IMPL *session, WT_ITEM *stop, uint32_t slot, WT_STUFF *ss)
{
WT_BTREE *btree;
WT_DECL_ITEM(dsk);
WT_DECL_ITEM(key);
WT_DECL_RET;
WT_PAGE *page;
WT_ROW *rip;
WT_TRACK *trk;
uint32_t i;
int cmp, found;
btree = S2BT(session);
page = NULL;
found = 0;
trk = ss->pages[slot];
/*
* If we deleted an initial piece of the WT_TRACK name space, it may no
* longer be in the right location.
*
* For example, imagine page #1 has the key range 30-50, it split, and
* we wrote page #2 with key range 30-40, and page #3 key range with
* 40-50, where pages #2 and #3 have larger LSNs than page #1. When the
* key ranges were sorted, page #2 came first, then page #1 (because of
* their earlier start keys than page #3), and page #2 came before page
* #1 because of its LSN. When we resolve the overlap between page #2
* and page #1, we truncate the initial key range of page #1, and it now
* sorts after page #3, because it has the same starting key of 40, and
* a lower LSN.
*
* First, update the WT_TRACK start key based on the specified stop key.
*
* Read and instantiate the WT_TRACK page (we don't have to verify the
* page, nor do we have to be quiet on error, we've already read this
* page successfully).
*/
WT_RET(__wt_scr_alloc(session, trk->trk_size, &dsk));
WT_ERR(__wt_bt_read(session, dsk, trk->trk_addr, trk->trk_addr_size));
WT_ERR(__wt_page_inmem(session, NULL, dsk->mem, 0, &page));
/*
* Walk the page, looking for a key sorting greater than the specified
* stop key -- that's our new start key.
*/
WT_ERR(__wt_scr_alloc(session, 0, &key));
WT_ROW_FOREACH(page, rip, i) {
WT_ERR(__wt_row_leaf_key(session, page, rip, key, 0));
WT_ERR(__wt_compare(session, btree->collator, key, stop, &cmp));
if (cmp > 0) {
found = 1;
break;
}
}
/*
* We know that at least one key on the page sorts after the specified
* stop key, otherwise the page would have entirely overlapped and we
* would have discarded it, we wouldn't be here. Therefore, this test
* is safe. (But, it never hurts to check.)
*/
WT_ERR_TEST(!found, WT_ERROR);
WT_ERR(__slvg_key_copy(session, &trk->row_start, key));
/*
* We may need to re-sort some number of elements in the list. Walk
* forward in the list until reaching an entry which cannot overlap
* the adjusted entry. If it's more than a single slot, re-sort the
* entries.
*/
for (i = slot + 1; i < ss->pages_next; ++i) {
if (ss->pages[i] == NULL)
continue;
WT_ERR(__wt_compare(session,
btree->collator, SLOT_START(i), &trk->row_stop, &cmp));
if (cmp > 0)
break;
}
i -= slot;
if (i > 1)
qsort(ss->pages + slot, (size_t)i,
sizeof(WT_TRACK *), __slvg_trk_compare_key);
err: if (page != NULL)
__wt_page_out(session, &page);
__wt_scr_free(session, &dsk);
__wt_scr_free(session, &key);
return (ret);
}
/*
* __slvg_row_build_internal --
* Build a row-store in-memory page that references all of the leaf
* pages we've found.
*/
static int
__slvg_row_build_internal(
WT_SESSION_IMPL *session, uint32_t leaf_cnt, WT_STUFF *ss)
{
WT_ADDR *addr;
WT_DECL_RET;
WT_PAGE *page;
WT_PAGE_INDEX *pindex;
WT_REF *ref, **refp;
WT_TRACK *trk;
uint32_t i;
addr = NULL;
/* Allocate a row-store root (internal) page and fill it in. */
WT_RET(
__wt_page_alloc(session, WT_PAGE_ROW_INT, 0, leaf_cnt, 1, &page));
WT_ERR(__slvg_modify_init(session, page));
pindex = WT_INTL_INDEX_COPY(page);
for (refp = pindex->index, i = 0; i < ss->pages_next; ++i) {
if ((trk = ss->pages[i]) == NULL)
continue;
ref = *refp++;
ref->home = page;
ref->page = NULL;
WT_ERR(__wt_calloc_one(session, &addr));
WT_ERR(__wt_strndup(
session, trk->trk_addr, trk->trk_addr_size, &addr->addr));
addr->size = trk->trk_addr_size;
addr->type =
trk->trk_ovfl_cnt == 0 ? WT_ADDR_LEAF_NO : WT_ADDR_LEAF;
ref->addr = addr;
addr = NULL;
__wt_ref_key_clear(ref);
ref->state = WT_REF_DISK;
/*
* If the page's key range is unmodified from when we read it
* (in other words, we didn't merge part of this page with
* another page), we can use the page without change, and the
* only thing we need to do is mark all overflow records the
* page references as in-use.
*
* If we did merge with another page, we have to build a page
* reflecting the updated key range. Note, that requires an
* additional pass to free the merge page's backing blocks.
*/
if (F_ISSET(trk, WT_TRACK_MERGE)) {
ss->merge_free = 1;
WT_ERR(__slvg_row_build_leaf(session, trk, ref, ss));
} else {
WT_ERR(__wt_row_ikey_incr(session, page, 0,
trk->row_start.data, trk->row_start.size, ref));
WT_ERR(__slvg_ovfl_ref_all(session, trk));
}
++ref;
}
__wt_root_ref_init(&ss->root_ref, page, 0);
if (0) {
err: if (addr != NULL)
__wt_free(session, addr);
__wt_page_out(session, &page);
}
return (ret);
}
/*
* __slvg_row_build_leaf --
* Build a row-store leaf page for a merged page.
*/
static int
__slvg_row_build_leaf(
WT_SESSION_IMPL *session, WT_TRACK *trk, WT_REF *ref, WT_STUFF *ss)
{
WT_BTREE *btree;
WT_DECL_ITEM(key);
WT_DECL_RET;
WT_PAGE *page;
WT_ROW *rip;
WT_SALVAGE_COOKIE *cookie, _cookie;
uint32_t i, skip_start, skip_stop;
int cmp;
btree = S2BT(session);
page = NULL;
cookie = &_cookie;
WT_CLEAR(*cookie);
/* Allocate temporary space in which to instantiate the keys. */
WT_RET(__wt_scr_alloc(session, 0, &key));
/* Get the original page, including the full in-memory setup. */
WT_ERR(__wt_page_in(session, ref, 0));
page = ref->page;
/*
* Figure out how many page keys we want to take and how many we want
* to skip.
*
* If checking the starting range key, the key we're searching for will
* be equal to the starting range key. This is because we figured out
* the true merged-page start key as part of discarding initial keys
* from the page (see the __slvg_row_range_overlap function, and its
* calls to __slvg_row_trk_update_start for more information).
*
* If checking the stopping range key, we want the keys on the page that
* are less-than the stopping range key. This is because we copied a
* key from another page to define this page's stop range: that page is
* the page that owns the "equal to" range space.
*/
skip_start = skip_stop = 0;
if (F_ISSET(trk, WT_TRACK_CHECK_START))
WT_ROW_FOREACH(page, rip, i) {
WT_ERR(__wt_row_leaf_key(session, page, rip, key, 0));
/*
* >= is correct: see the comment above.
*/
WT_ERR(__wt_compare(session,
btree->collator, key, &trk->row_start, &cmp));
if (cmp >= 0)
break;
if (WT_VERBOSE_ISSET(session, WT_VERB_SALVAGE)) {
WT_ERR(__wt_buf_set_printable(session,
ss->tmp1, key->data, key->size));
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s merge discarding leading key %.*s",
__wt_addr_string(session,
trk->trk_addr, trk->trk_addr_size,
ss->tmp2), (int)ss->tmp1->size,
(char *)ss->tmp1->data));
}
++skip_start;
}
if (F_ISSET(trk, WT_TRACK_CHECK_STOP))
WT_ROW_FOREACH_REVERSE(page, rip, i) {
WT_ERR(__wt_row_leaf_key(session, page, rip, key, 0));
/*
* < is correct: see the comment above.
*/
WT_ERR(__wt_compare(session,
btree->collator, key, &trk->row_stop, &cmp));
if (cmp < 0)
break;
if (WT_VERBOSE_ISSET(session, WT_VERB_SALVAGE)) {
WT_ERR(__wt_buf_set_printable(session,
ss->tmp1, key->data, key->size));
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s merge discarding trailing key %.*s",
__wt_addr_string(session,
trk->trk_addr, trk->trk_addr_size,
ss->tmp2), (int)ss->tmp1->size,
(char *)ss->tmp1->data));
}
++skip_stop;
}
/* We should have selected some entries, but not the entire page. */
WT_ASSERT(session,
skip_start + skip_stop > 0 &&
skip_start + skip_stop < page->pg_row_entries);
/*
* Take a copy of this page's first key to define the start of
* its range. The key may require processing, otherwise, it's
* a copy from the page.
*/
rip = page->pg_row_d + skip_start;
WT_ERR(__wt_row_leaf_key(session, page, rip, key, 0));
WT_ERR(__wt_row_ikey_incr(
session, ref->home, 0, key->data, key->size, ref));
/* Set the referenced flag on overflow pages we're using. */
if (trk->trk_ovfl_cnt != 0)
WT_ERR(__slvg_row_ovfl(session,
trk, page, skip_start, page->pg_row_entries - skip_stop));
/*
* Change the page to reflect the correct record count: there is no
* need to copy anything on the page itself, the entries value limits
* the number of page items.
*/
page->pg_row_entries -= skip_stop;
cookie->skip = skip_start;
/*
* We can't discard the original blocks associated with this page now.
* (The problem is we don't want to overwrite any original information
* until the salvage run succeeds -- if we free the blocks now, the next
* merge page we write might allocate those blocks and overwrite them,
* and should the salvage run eventually fail, the original information
* would have been lost.) Clear the reference addr so eviction doesn't
* free the underlying blocks.
*/
__wt_free(session, ((WT_ADDR *)ref->addr)->addr);
__wt_free(session, ref->addr);
ref->addr = NULL;
/* Write the new version of the leaf page to disk. */
WT_ERR(__slvg_modify_init(session, page));
WT_ERR(__wt_reconcile(session, ref, cookie, WT_SKIP_UPDATE_ERR));
/* Reset the page. */
page->pg_row_entries += skip_stop;
/*
* Discard our hazard pointer and evict the page, updating the
* parent's reference.
*/
ret = __wt_page_release(session, ref, 0);
if (ret == 0)
ret = __wt_evict(session, ref, 1);
if (0) {
err: WT_TRET(__wt_page_release(session, ref, 0));
}
__wt_scr_free(session, &key);
return (ret);
}
/*
* __slvg_row_ovfl_single --
* Find a single overflow record in the merge page's list, and mark it as
* referenced.
*/
static int
__slvg_row_ovfl_single(WT_SESSION_IMPL *session, WT_TRACK *trk, WT_CELL *cell)
{
WT_CELL_UNPACK unpack;
WT_TRACK *ovfl;
uint32_t i;
/* Unpack the cell, and check if it's an overflow record. */
__wt_cell_unpack(cell, &unpack);
if (unpack.type != WT_CELL_KEY_OVFL &&
unpack.type != WT_CELL_VALUE_OVFL)
return (0);
/*
* Search the list of overflow records for this page -- we should find
* exactly one match, and we mark it as referenced.
*/
for (i = 0; i < trk->trk_ovfl_cnt; ++i) {
ovfl = trk->ss->ovfl[trk->trk_ovfl_slot[i]];
if (unpack.size == ovfl->trk_addr_size &&
memcmp(unpack.data, ovfl->trk_addr, unpack.size) == 0)
return (__slvg_ovfl_ref(session, ovfl, 1));
}
WT_PANIC_RET(session,
EINVAL, "overflow record at row-store page merge not found");
}
/*
* __slvg_row_ovfl --
* Mark overflow items referenced by the merged page.
*/
static int
__slvg_row_ovfl(WT_SESSION_IMPL *session,
WT_TRACK *trk, WT_PAGE *page, uint32_t start, uint32_t stop)
{
WT_CELL *cell;
WT_ROW *rip;
void *copy;
/*
* We're merging a row-store page, and we took some number of records,
* figure out which (if any) overflow records we used.
*/
for (rip = page->pg_row_d + start; start < stop; ++start, ++rip) {
copy = WT_ROW_KEY_COPY(rip);
(void)__wt_row_leaf_key_info(
page, copy, NULL, &cell, NULL, NULL);
if (cell != NULL)
WT_RET(__slvg_row_ovfl_single(session, trk, cell));
cell = __wt_row_leaf_value_cell(page, rip, NULL);
if (cell != NULL)
WT_RET(__slvg_row_ovfl_single(session, trk, cell));
}
return (0);
}
/*
* __slvg_trk_compare_addr --
* Compare two WT_TRACK array entries by address cookie.
*/
static int
__slvg_trk_compare_addr(const void *a, const void *b)
{
WT_DECL_RET;
WT_TRACK *a_trk, *b_trk;
size_t len;
a_trk = *(WT_TRACK **)a;
b_trk = *(WT_TRACK **)b;
/*
* We don't care about the order because these are opaque cookies --
* we're just sorting them so we can binary search instead of linear
* search.
*/
len = WT_MIN(a_trk->trk_addr_size, b_trk->trk_addr_size);
ret = memcmp(a_trk->trk_addr, b_trk->trk_addr, len);
if (ret == 0)
ret = a_trk->trk_addr_size > b_trk->trk_addr_size ? -1 : 1;
return (ret);
}
/*
* __slvg_ovfl_compare --
* Bsearch comparison routine for the overflow array.
*/
static int
__slvg_ovfl_compare(const void *a, const void *b)
{
WT_ADDR *addr;
WT_DECL_RET;
WT_TRACK *trk;
size_t len;
addr = (WT_ADDR *)a;
trk = *(WT_TRACK **)b;
len = WT_MIN(trk->trk_addr_size, addr->size);
ret = memcmp(addr->addr, trk->trk_addr, len);
if (ret == 0 && addr->size != trk->trk_addr_size)
ret = addr->size < trk->trk_addr_size ? -1 : 1;
return (ret);
}
/*
* __slvg_ovfl_reconcile --
* Review relationships between leaf pages and the overflow pages, delete
* leaf pages until there's a one-to-one relationship between leaf and overflow
* pages.
*/
static int
__slvg_ovfl_reconcile(WT_SESSION_IMPL *session, WT_STUFF *ss)
{
WT_ADDR *addr;
WT_DECL_RET;
WT_TRACK **searchp, *trk;
uint32_t i, j, *slot;
slot = NULL;
/*
* If an overflow page is referenced more than once, discard leaf pages
* with the lowest LSNs until overflow pages are only referenced once.
*
* This requires sorting the page list by LSN, and the overflow array
* by address cookie.
*/
qsort(ss->pages,
(size_t)ss->pages_next, sizeof(WT_TRACK *), __slvg_trk_compare_gen);
qsort(ss->ovfl,
(size_t)ss->ovfl_next, sizeof(WT_TRACK *), __slvg_trk_compare_addr);
/*
* Walk the list of pages and discard any pages referencing non-existent
* overflow pages or referencing overflow pages also referenced by pages
* with higher LSNs. Our caller sorted the page list by LSN, high to
* low, so we don't have to do explicit testing of the page LSNs, the
* first page to reference an overflow page is the best page to own it.
*/
for (i = 0; i < ss->pages_next; ++i) {
if ((trk = ss->pages[i]) == NULL || trk->trk_ovfl_cnt == 0)
continue;
WT_ERR(__wt_calloc_def(session, trk->trk_ovfl_cnt, &slot));
for (j = 0; j < trk->trk_ovfl_cnt; ++j) {
addr = &trk->trk_ovfl_addr[j];
searchp = bsearch(addr, ss->ovfl, ss->ovfl_next,
sizeof(WT_TRACK *), __slvg_ovfl_compare);
/*
* If the overflow page doesn't exist or if another page
* has already claimed it, this leaf page isn't usable.
*/
if (searchp != NULL &&
!F_ISSET(*searchp, WT_TRACK_OVFL_REFD)) {
/*
* Convert each block address into a slot in the
* list of overflow pages as we go.
*/
slot[j] = (uint32_t)(searchp - ss->ovfl);
F_SET(*searchp, WT_TRACK_OVFL_REFD);
continue;
}
WT_ERR(__wt_verbose(session, WT_VERB_SALVAGE,
"%s references unavailable overflow page %s",
__wt_addr_string(session,
trk->trk_addr, trk->trk_addr_size, ss->tmp1),
__wt_addr_string(session,
addr->addr, addr->size, ss->tmp2)));
/*
* Clear the "referenced" flag for any overflow pages
* already claimed by this leaf page some other page
* might claim them.
*/
while (j > 0)
F_CLR(ss->ovfl[slot[--j]], WT_TRACK_OVFL_REFD);
trk = NULL;
WT_ERR(__slvg_trk_free(session, &ss->pages[i], 1));
break;
}
/*
* We now have a reference to the overflow WT_TRACK, and so no
* longer need the page's address array, discard it. Note, we
* potentially freed the WT_TRACK in the loop above, check it's
* still valid.
*/
if (trk == NULL)
__wt_free(session, slot);
else {
__slvg_trk_free_addr(session, trk);
trk->trk_ovfl_slot = slot;
slot = NULL;
}
}
return (0);
err: __wt_free(session, slot);
return (ret);
}
/*
* __slvg_trk_compare_key --
* Compare two WT_TRACK array entries by key, and secondarily, by LSN.
*/
static int
__slvg_trk_compare_key(const void *a, const void *b)
{
WT_SESSION_IMPL *session;
WT_TRACK *a_trk, *b_trk;
uint64_t a_gen, a_recno, b_gen, b_recno;
int cmp;
a_trk = *(WT_TRACK **)a;
b_trk = *(WT_TRACK **)b;
if (a_trk == NULL)
return (b_trk == NULL ? 0 : 1);
if (b_trk == NULL)
return (-1);
switch (a_trk->ss->page_type) {
case WT_PAGE_COL_FIX:
case WT_PAGE_COL_VAR:
a_recno = a_trk->col_start;
b_recno = b_trk->col_start;
if (a_recno == b_recno)
break;
if (a_recno > b_recno)
return (1);
if (a_recno < b_recno)
return (-1);
break;
case WT_PAGE_ROW_LEAF:
/*
* XXX
* __wt_compare can potentially fail, and we're ignoring that
* error because this routine is called as an underlying qsort
* routine.
*/
session = a_trk->ss->session;
(void)__wt_compare(session, S2BT(session)->collator,
&a_trk->row_start, &b_trk->row_start, &cmp);
if (cmp != 0)
return (cmp);
break;
}
/*
* If the primary keys compare equally, differentiate based on LSN.
* Sort from highest LSN to lowest, that is, the earlier pages in
* the array are more desirable.
*/
a_gen = a_trk->trk_gen;
b_gen = b_trk->trk_gen;
return (a_gen > b_gen ? -1 : (a_gen < b_gen ? 1 : 0));
}
/*
* __slvg_trk_compare_gen --
* Compare two WT_TRACK array entries by LSN.
*/
static int
__slvg_trk_compare_gen(const void *a, const void *b)
{
WT_TRACK *a_trk, *b_trk;
uint64_t a_gen, b_gen;
a_trk = *(WT_TRACK **)a;
b_trk = *(WT_TRACK **)b;
/*
* Sort from highest LSN to lowest, that is, the earlier pages in the
* array are more desirable.
*/
a_gen = a_trk->trk_gen;
b_gen = b_trk->trk_gen;
return (a_gen > b_gen ? -1 : (a_gen < b_gen ? 1 : 0));
}
/*
* __slvg_merge_block_free --
* Clean up backing file and overflow blocks after the merge phase.
*/
static int
__slvg_merge_block_free(WT_SESSION_IMPL *session, WT_STUFF *ss)
{
WT_TRACK *trk;
uint32_t i;
/* Free any underlying file blocks for merged pages. */
for (i = 0; i < ss->pages_next; ++i) {
if ((trk = ss->pages[i]) == NULL)
continue;
if (F_ISSET(trk, WT_TRACK_MERGE))
WT_RET(__slvg_trk_free(session, &ss->pages[i], 1));
}
/* Free any unused overflow records. */
return (__slvg_ovfl_discard(session, ss));
}
/*
* __slvg_ovfl_ref --
* Reference an overflow page, checking for multiple references.
*/
static int
__slvg_ovfl_ref(WT_SESSION_IMPL *session, WT_TRACK *trk, int multi_panic)
{
if (F_ISSET(trk, WT_TRACK_OVFL_REFD)) {
if (!multi_panic)
return (EBUSY);
WT_PANIC_RET(session, EINVAL,
"overflow record unexpectedly referenced multiple times "
"during leaf page merge");
}
F_SET(trk, WT_TRACK_OVFL_REFD);
return (0);
}
/*
* __slvg_ovfl_ref_all --
* Reference all of the page's overflow pages.
*/
static int
__slvg_ovfl_ref_all(WT_SESSION_IMPL *session, WT_TRACK *trk)
{
uint32_t i;
for (i = 0; i < trk->trk_ovfl_cnt; ++i)
WT_RET(__slvg_ovfl_ref(
session, trk->ss->ovfl[trk->trk_ovfl_slot[i]], 1));
return (0);
}
/*
* __slvg_ovfl_discard --
* Discard unused overflow pages.
*/
static int
__slvg_ovfl_discard(WT_SESSION_IMPL *session, WT_STUFF *ss)
{
WT_TRACK *trk;
uint32_t i;
/*
* Walk the overflow page array: if an overflow page isn't referenced,
* add its file blocks to the free list.
*
* Clear the reference flag (it's reused to figure out if the overflow
* record is referenced, but never used, by merged pages).
*/
for (i = 0; i < ss->ovfl_next; ++i) {
if ((trk = ss->ovfl[i]) == NULL)
continue;
if (F_ISSET(trk, WT_TRACK_OVFL_REFD)) {
F_CLR(trk, WT_TRACK_OVFL_REFD);
continue;
}
WT_RET(__wt_verbose(session, WT_VERB_SALVAGE,
"%s unused overflow page",
__wt_addr_string(
session, trk->trk_addr, trk->trk_addr_size, ss->tmp1)));
WT_RET(__slvg_trk_free(session, &ss->ovfl[i], 1));
}
return (0);
}
/*
* __slvg_cleanup --
* Discard memory allocated to the page and overflow arrays.
*/
static int
__slvg_cleanup(WT_SESSION_IMPL *session, WT_STUFF *ss)
{
uint32_t i;
/* Discard the leaf page array. */
for (i = 0; i < ss->pages_next; ++i)
if (ss->pages[i] != NULL)
WT_RET(__slvg_trk_free(session, &ss->pages[i], 0));
__wt_free(session, ss->pages);
/* Discard the ovfl page array. */
for (i = 0; i < ss->ovfl_next; ++i)
if (ss->ovfl[i] != NULL)
WT_RET(__slvg_trk_free(session, &ss->ovfl[i], 0));
__wt_free(session, ss->ovfl);
return (0);
}
/*
* __slvg_trk_free_addr --
* Discard address information.
*/
static void
__slvg_trk_free_addr(WT_SESSION_IMPL *session, WT_TRACK *trk)
{
uint32_t i;
if (trk->trk_ovfl_addr != NULL) {
for (i = 0; i < trk->trk_ovfl_cnt; ++i)
__wt_free(session, trk->trk_ovfl_addr[i].addr);
__wt_free(session, trk->trk_ovfl_addr);
}
}
/*
* __slvg_trk_free_block --
* Discard underlying blocks.
*/
static int
__slvg_trk_free_block(WT_SESSION_IMPL *session, WT_TRACK *trk)
{
WT_BM *bm;
bm = S2BT(session)->bm;
/*
* If freeing underlying file blocks or overflow pages, this is a page
* we were tracking but eventually decided not to use.
*/
WT_RET(__wt_verbose(session, WT_VERB_SALVAGE,
"%s blocks discarded: discard freed file bytes %" PRIu32,
__wt_addr_string(session,
trk->trk_addr, trk->trk_addr_size, trk->ss->tmp1), trk->trk_size));
return (bm->free(bm, session, trk->trk_addr, trk->trk_addr_size));
}
/*
* __slvg_trk_free --
* Discard a WT_TRACK structure and (optionally) its underlying blocks.
*/
static int
__slvg_trk_free(WT_SESSION_IMPL *session, WT_TRACK **trkp, int free_on_last_ref)
{
WT_TRACK *trk;
trk = *trkp;
*trkp = NULL;
/*
* If we're the last user of shared information, clean up.
*/
WT_ASSERT(session, trk->shared->ref > 0);
if (--trk->shared->ref == 0) {
/*
* If the free-on-last-ref flag is set, this chunk isn't going
* to use the backing physical blocks. As we're the last user
* of those blocks, nobody is going to use them and they can be
* discarded.
*/
if (free_on_last_ref)
WT_RET(__slvg_trk_free_block(session, trk));
__wt_free(session, trk->trk_addr);
__slvg_trk_free_addr(session, trk);
__wt_free(session, trk->trk_ovfl_slot);
__wt_free(session, trk->shared);
}
if (trk->ss->page_type == WT_PAGE_ROW_LEAF) {
__wt_buf_free(session, &trk->row_start);
__wt_buf_free(session, &trk->row_stop);
}
__wt_free(session, trk);
return (0);
}
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