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/*-
* Copyright (c) 2014-2016 MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
/*
* Supported btree formats: the "current" version is the maximum supported
* major/minor versions.
*/
#define WT_BTREE_MAJOR_VERSION_MIN 1 /* Oldest version supported */
#define WT_BTREE_MINOR_VERSION_MIN 1
#define WT_BTREE_MAJOR_VERSION_MAX 1 /* Newest version supported */
#define WT_BTREE_MINOR_VERSION_MAX 1
/*
* The maximum btree leaf and internal page size is 512MB (2^29). The limit
* is enforced in software, it could be larger, specifically, the underlying
* default block manager can support 4GB (2^32). Currently, the maximum page
* size must accommodate our dependence on the maximum page size fitting into
* a number of bits less than 32; see the row-store page key-lookup functions
* for the magic.
*/
#define WT_BTREE_PAGE_SIZE_MAX (512 * WT_MEGABYTE)
/*
* The length of variable-length column-store values and row-store keys/values
* are stored in a 4B type, so the largest theoretical key/value item is 4GB.
* However, in the WT_UPDATE structure we use the UINT32_MAX size as a "deleted"
* flag, and second, the size of an overflow object is constrained by what an
* underlying block manager can actually write. (For example, in the default
* block manager, writing an overflow item includes the underlying block's page
* header and block manager specific structure, aligned to an allocation-sized
* unit). The btree engine limits the size of a single object to (4GB - 1KB);
* that gives us additional bytes if we ever want to store a structure length
* plus the object size in 4B, or if we need additional flag values. Attempts
* to store large key/value items in the tree trigger an immediate check to the
* block manager, to make sure it can write the item. Storing 4GB objects in a
* btree borders on clinical insanity, anyway.
*
* Record numbers are stored in 64-bit unsigned integers, meaning the largest
* record number is "really, really big".
*/
#define WT_BTREE_MAX_OBJECT_SIZE (UINT32_MAX - 1024)
/*
* A location in a file is a variable-length cookie, but it has a maximum size
* so it's easy to create temporary space in which to store them. (Locations
* can't be much larger than this anyway, they must fit onto the minimum size
* page because a reference to an overflow page is itself a location.)
*/
#define WT_BTREE_MAX_ADDR_COOKIE 255 /* Maximum address cookie */
/* Evict pages if we see this many consecutive deleted records. */
#define WT_BTREE_DELETE_THRESHOLD 1000
/*
* WT_BTREE --
* A btree handle.
*/
struct __wt_btree {
WT_DATA_HANDLE *dhandle;
WT_CKPT *ckpt; /* Checkpoint information */
enum { BTREE_COL_FIX=1, /* Fixed-length column store */
BTREE_COL_VAR=2, /* Variable-length column store */
BTREE_ROW=3 /* Row-store */
} type; /* Type */
const char *key_format; /* Key format */
const char *value_format; /* Value format */
uint8_t bitcnt; /* Fixed-length field size in bits */
WT_COLLATOR *collator; /* Row-store comparator */
int collator_owned; /* The collator needs to be freed */
uint32_t id; /* File ID, for logging */
uint32_t key_gap; /* Row-store prefix key gap */
uint32_t allocsize; /* Allocation size */
uint32_t maxintlpage; /* Internal page max size */
uint32_t maxintlkey; /* Internal page max key size */
uint32_t maxleafpage; /* Leaf page max size */
uint32_t maxleafkey; /* Leaf page max key size */
uint32_t maxleafvalue; /* Leaf page max value size */
uint64_t maxmempage; /* In-memory page max size */
uint64_t splitmempage; /* In-memory split trigger size */
void *huffman_key; /* Key huffman encoding */
void *huffman_value; /* Value huffman encoding */
enum { CKSUM_ON=1, /* On */
CKSUM_OFF=2, /* Off */
CKSUM_UNCOMPRESSED=3 /* Uncompressed blocks only */
} checksum; /* Checksum configuration */
/*
* Reconciliation...
*/
u_int dictionary; /* Dictionary slots */
bool internal_key_truncate; /* Internal key truncate */
int maximum_depth; /* Maximum tree depth */
bool prefix_compression; /* Prefix compression */
u_int prefix_compression_min; /* Prefix compression min */
#define WT_SPLIT_DEEPEN_MIN_CHILD_DEF 10000
u_int split_deepen_min_child; /* Minimum entries to deepen tree */
#define WT_SPLIT_DEEPEN_PER_CHILD_DEF 100
u_int split_deepen_per_child; /* Entries per child when deepened */
int split_pct; /* Split page percent */
WT_COMPRESSOR *compressor; /* Page compressor */
WT_KEYED_ENCRYPTOR *kencryptor; /* Page encryptor */
WT_RWLOCK *ovfl_lock; /* Overflow lock */
uint64_t last_recno; /* Column-store last record number */
WT_REF root; /* Root page reference */
int modified; /* If the tree ever modified */
bool bulk_load_ok; /* Bulk-load is a possibility */
WT_BM *bm; /* Block manager reference */
u_int block_header; /* WT_PAGE_HEADER_BYTE_SIZE */
uint64_t checkpoint_gen; /* Checkpoint generation */
uint64_t rec_max_txn; /* Maximum txn seen (clean trees) */
uint64_t write_gen; /* Write generation */
WT_REF *evict_ref; /* Eviction thread's location */
uint64_t evict_priority; /* Relative priority of cached pages */
u_int evict_walk_period; /* Skip this many LRU walks */
u_int evict_walk_skips; /* Number of walks skipped */
u_int evict_disabled; /* Eviction disabled count */
volatile uint32_t evict_busy; /* Count of threads in eviction */
enum {
WT_CKPT_OFF, WT_CKPT_PREPARE, WT_CKPT_RUNNING
} checkpointing; /* Checkpoint in progress */
/*
* We flush pages from the tree (in order to make checkpoint faster),
* without a high-level lock. To avoid multiple threads flushing at
* the same time, lock the tree.
*/
WT_SPINLOCK flush_lock; /* Lock to flush the tree's pages */
/* Flags values up to 0xff are reserved for WT_DHANDLE_* */
#define WT_BTREE_BULK 0x00100 /* Bulk-load handle */
#define WT_BTREE_IN_MEMORY 0x00200 /* Cache-resident object */
#define WT_BTREE_LOOKASIDE 0x00400 /* Look-aside table */
#define WT_BTREE_NO_CHECKPOINT 0x00800 /* Disable checkpoints */
#define WT_BTREE_NO_EVICTION 0x01000 /* Disable eviction */
#define WT_BTREE_NO_LOGGING 0x02000 /* Disable logging */
#define WT_BTREE_REBALANCE 0x04000 /* Handle is for rebalance */
#define WT_BTREE_SALVAGE 0x08000 /* Handle is for salvage */
#define WT_BTREE_SKIP_CKPT 0x10000 /* Handle skipped checkpoint */
#define WT_BTREE_UPGRADE 0x20000 /* Handle is for upgrade */
#define WT_BTREE_VERIFY 0x40000 /* Handle is for verify */
uint32_t flags;
};
/* Flags that make a btree handle special (not for normal use). */
#define WT_BTREE_SPECIAL_FLAGS \
(WT_BTREE_BULK | WT_BTREE_REBALANCE | \
WT_BTREE_SALVAGE | WT_BTREE_UPGRADE | WT_BTREE_VERIFY)
/*
* WT_SALVAGE_COOKIE --
* Encapsulation of salvage information for reconciliation.
*/
struct __wt_salvage_cookie {
uint64_t missing; /* Initial items to create */
uint64_t skip; /* Initial items to skip */
uint64_t take; /* Items to take */
bool done; /* Ignore the rest */
};
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