/***************************************************************************** Copyright (c) 1997, 2012, Oracle and/or its affiliates. All Rights Reserved. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA *****************************************************************************/ /**************************************************//** @file row/row0vers.cc Row versions Created 2/6/1997 Heikki Tuuri *******************************************************/ #include "row0vers.h" #ifdef UNIV_NONINL #include "row0vers.ic" #endif #include "dict0dict.h" #include "dict0boot.h" #include "btr0btr.h" #include "mach0data.h" #include "trx0rseg.h" #include "trx0trx.h" #include "trx0roll.h" #include "trx0undo.h" #include "trx0purge.h" #include "trx0rec.h" #include "que0que.h" #include "row0row.h" #include "row0upd.h" #include "rem0cmp.h" #include "read0read.h" #include "lock0lock.h" /*****************************************************************//** Finds out if an active transaction has inserted or modified a secondary index record. @return 0 if committed, else the active transaction id; NOTE that this function can return false positives but never false negatives. The caller must confirm all positive results by calling trx_is_active() while holding lock_sys->mutex. */ UNIV_INLINE trx_id_t row_vers_impl_x_locked_low( /*=======================*/ const rec_t* clust_rec, /*!< in: clustered index record */ dict_index_t* clust_index, /*!< in: the clustered index */ const rec_t* rec, /*!< in: secondary index record */ dict_index_t* index, /*!< in: the secondary index */ const ulint* offsets, /*!< in: rec_get_offsets(rec, index) */ mtr_t* mtr) /*!< in/out: mini-transaction */ { trx_id_t trx_id; ibool corrupt; ulint comp; ulint rec_del; const rec_t* version; rec_t* prev_version = NULL; ulint* clust_offsets; mem_heap_t* heap; ut_ad(rec_offs_validate(rec, index, offsets)); heap = mem_heap_create(1024); clust_offsets = rec_get_offsets( clust_rec, clust_index, NULL, ULINT_UNDEFINED, &heap); trx_id = row_get_rec_trx_id(clust_rec, clust_index, clust_offsets); corrupt = FALSE; if (!trx_rw_is_active(trx_id, &corrupt)) { /* The transaction that modified or inserted clust_rec is no longer active, or it is corrupt: no implicit lock on rec */ if (corrupt) { lock_report_trx_id_insanity( trx_id, clust_rec, clust_index, clust_offsets, trx_sys_get_max_trx_id()); } mem_heap_free(heap); return(0); } comp = page_rec_is_comp(rec); ut_ad(index->table == clust_index->table); ut_ad(!!comp == dict_table_is_comp(index->table)); ut_ad(!comp == !page_rec_is_comp(clust_rec)); rec_del = rec_get_deleted_flag(rec, comp); /* We look up if some earlier version, which was modified by the trx_id transaction, of the clustered index record would require rec to be in a different state (delete marked or unmarked, or have different field values, or not existing). If there is such a version, then rec was modified by the trx_id transaction, and it has an implicit x-lock on rec. Note that if clust_rec itself would require rec to be in a different state, then the trx_id transaction has not yet had time to modify rec, and does not necessarily have an implicit x-lock on rec. */ for (version = clust_rec;; version = prev_version) { row_ext_t* ext; const dtuple_t* row; dtuple_t* entry; ulint vers_del; trx_id_t prev_trx_id; mem_heap_t* old_heap = heap; /* We keep the semaphore in mtr on the clust_rec page, so that no other transaction can update it and get an implicit x-lock on rec until mtr_commit(mtr). */ heap = mem_heap_create(1024); trx_undo_prev_version_build( clust_rec, mtr, version, clust_index, clust_offsets, heap, &prev_version); /* Free version and clust_offsets. */ mem_heap_free(old_heap); if (prev_version == NULL) { /* clust_rec should be a fresh insert, because no previous version was found or the transaction has committed. The caller has to recheck as the synopsis of this function states, whether trx_id is active or not. */ break; } clust_offsets = rec_get_offsets( prev_version, clust_index, NULL, ULINT_UNDEFINED, &heap); vers_del = rec_get_deleted_flag(prev_version, comp); prev_trx_id = row_get_rec_trx_id(prev_version, clust_index, clust_offsets); /* The stack of versions is locked by mtr. Thus, it is safe to fetch the prefixes for externally stored columns. */ row = row_build(ROW_COPY_POINTERS, clust_index, prev_version, clust_offsets, NULL, NULL, NULL, &ext, heap); entry = row_build_index_entry(row, ext, index, heap); /* entry may be NULL if a record was inserted in place of a deleted record, and the BLOB pointers of the new record were not initialized yet. But in that case, prev_version should be NULL. */ ut_a(entry != NULL); /* If we get here, we know that the trx_id transaction modified prev_version. Let us check if prev_version would require rec to be in a different state. */ /* The previous version of clust_rec must be accessible, because clust_rec was not a fresh insert. There is no guarantee that the transaction is still active. */ /* We check if entry and rec are identified in the alphabetical ordering */ if (!trx_rw_is_active(trx_id, &corrupt)) { /* Transaction no longer active: no implicit x-lock. This situation should only be possible because we are not holding lock_sys->mutex. */ ut_ad(!lock_mutex_own()); if (corrupt) { lock_report_trx_id_insanity( trx_id, prev_version, clust_index, clust_offsets, trx_sys_get_max_trx_id()); } trx_id = 0; break; } else if (0 == cmp_dtuple_rec(entry, rec, offsets)) { /* The delete marks of rec and prev_version should be equal for rec to be in the state required by prev_version */ if (rec_del != vers_del) { break; } /* It is possible that the row was updated so that the secondary index record remained the same in alphabetical ordering, but the field values changed still. For example, 'abc' -> 'ABC'. Check also that. */ dtuple_set_types_binary( entry, dtuple_get_n_fields(entry)); if (0 != cmp_dtuple_rec(entry, rec, offsets)) { break; } } else if (!rec_del) { /* The delete mark should be set in rec for it to be in the state required by prev_version */ break; } if (trx_id != prev_trx_id) { /* prev_version was the first version modified by the trx_id transaction: no implicit x-lock */ trx_id = 0; break; } } mem_heap_free(heap); return(trx_id); } /*****************************************************************//** Finds out if an active transaction has inserted or modified a secondary index record. @return 0 if committed, else the active transaction id; NOTE that this function can return false positives but never false negatives. The caller must confirm all positive results by calling trx_is_active() while holding lock_sys->mutex. */ UNIV_INTERN trx_id_t row_vers_impl_x_locked( /*===================*/ const rec_t* rec, /*!< in: record in a secondary index */ dict_index_t* index, /*!< in: the secondary index */ const ulint* offsets)/*!< in: rec_get_offsets(rec, index) */ { dict_index_t* clust_index; const rec_t* clust_rec; trx_id_t trx_id; mtr_t mtr; ut_ad(!lock_mutex_own()); ut_ad(!mutex_own(&trx_sys->mutex)); mtr_start(&mtr); /* Search for the clustered index record. The latch on the page of clust_rec locks the top of the stack of versions. The bottom of the version stack is not locked; oldest versions may disappear by the fact that transactions may be committed and collected by the purge. This is not a problem, because we are only interested in active transactions. */ clust_rec = row_get_clust_rec( BTR_SEARCH_LEAF, rec, index, &clust_index, &mtr); if (UNIV_UNLIKELY(!clust_rec)) { /* In a rare case it is possible that no clust rec is found for a secondary index record: if in row0umod.cc row_undo_mod_remove_clust_low() we have already removed the clust rec, while purge is still cleaning and removing secondary index records associated with earlier versions of the clustered index record. In that case there cannot be any implicit lock on the secondary index record, because an active transaction which has modified the secondary index record has also modified the clustered index record. And in a rollback we always undo the modifications to secondary index records before the clustered index record. */ trx_id = 0; } else { trx_id = row_vers_impl_x_locked_low( clust_rec, clust_index, rec, index, offsets, &mtr); } mtr_commit(&mtr); return(trx_id); } /*****************************************************************//** Finds out if we must preserve a delete marked earlier version of a clustered index record, because it is >= the purge view. @return TRUE if earlier version should be preserved */ UNIV_INTERN ibool row_vers_must_preserve_del_marked( /*==============================*/ trx_id_t trx_id, /*!< in: transaction id in the version */ mtr_t* mtr) /*!< in: mtr holding the latch on the clustered index record; it will also hold the latch on purge_view */ { #ifdef UNIV_SYNC_DEBUG ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED)); #endif /* UNIV_SYNC_DEBUG */ mtr_s_lock(&(purge_sys->latch), mtr); return(!read_view_sees_trx_id(purge_sys->view, trx_id)); } /*****************************************************************//** Finds out if a version of the record, where the version >= the current purge view, should have ientry as its secondary index entry. We check if there is any not delete marked version of the record where the trx id >= purge view, and the secondary index entry and ientry are identified in the alphabetical ordering; exactly in this case we return TRUE. @return TRUE if earlier version should have */ UNIV_INTERN ibool row_vers_old_has_index_entry( /*=========================*/ ibool also_curr,/*!< in: TRUE if also rec is included in the versions to search; otherwise only versions prior to it are searched */ const rec_t* rec, /*!< in: record in the clustered index; the caller must have a latch on the page */ mtr_t* mtr, /*!< in: mtr holding the latch on rec; it will also hold the latch on purge_view */ dict_index_t* index, /*!< in: the secondary index */ const dtuple_t* ientry) /*!< in: the secondary index entry */ { const rec_t* version; rec_t* prev_version; dict_index_t* clust_index; ulint* clust_offsets; mem_heap_t* heap; mem_heap_t* heap2; const dtuple_t* row; const dtuple_t* entry; ulint comp; ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX) || mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_S_FIX)); #ifdef UNIV_SYNC_DEBUG ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED)); #endif /* UNIV_SYNC_DEBUG */ clust_index = dict_table_get_first_index(index->table); comp = page_rec_is_comp(rec); ut_ad(!dict_table_is_comp(index->table) == !comp); heap = mem_heap_create(1024); clust_offsets = rec_get_offsets(rec, clust_index, NULL, ULINT_UNDEFINED, &heap); if (also_curr && !rec_get_deleted_flag(rec, comp)) { row_ext_t* ext; /* The top of the stack of versions is locked by the mtr holding a latch on the page containing the clustered index record. The bottom of the stack is locked by the fact that the purge_sys->view must 'overtake' any read view of an active transaction. Thus, it is safe to fetch the prefixes for externally stored columns. */ row = row_build(ROW_COPY_POINTERS, clust_index, rec, clust_offsets, NULL, NULL, NULL, &ext, heap); entry = row_build_index_entry(row, ext, index, heap); /* If entry == NULL, the record contains unset BLOB pointers. This must be a freshly inserted record. If this is called from row_purge_remove_sec_if_poss_low(), the thread will hold latches on the clustered index and the secondary index. Because the insert works in three steps: (1) insert the record to clustered index (2) store the BLOBs and update BLOB pointers (3) insert records to secondary indexes the purge thread can safely ignore freshly inserted records and delete the secondary index record. The thread that inserted the new record will be inserting the secondary index records. */ /* NOTE that we cannot do the comparison as binary fields because the row is maybe being modified so that the clustered index record has already been updated to a different binary value in a char field, but the collation identifies the old and new value anyway! */ if (entry && !dtuple_coll_cmp(ientry, entry)) { mem_heap_free(heap); return(TRUE); } } version = rec; for (;;) { heap2 = heap; heap = mem_heap_create(1024); trx_undo_prev_version_build(rec, mtr, version, clust_index, clust_offsets, heap, &prev_version); mem_heap_free(heap2); /* free version and clust_offsets */ if (!prev_version) { /* Versions end here */ mem_heap_free(heap); return(FALSE); } clust_offsets = rec_get_offsets(prev_version, clust_index, NULL, ULINT_UNDEFINED, &heap); if (!rec_get_deleted_flag(prev_version, comp)) { row_ext_t* ext; /* The stack of versions is locked by mtr. Thus, it is safe to fetch the prefixes for externally stored columns. */ row = row_build(ROW_COPY_POINTERS, clust_index, prev_version, clust_offsets, NULL, NULL, NULL, &ext, heap); entry = row_build_index_entry(row, ext, index, heap); /* If entry == NULL, the record contains unset BLOB pointers. This must be a freshly inserted record that we can safely ignore. For the justification, see the comments after the previous row_build_index_entry() call. */ /* NOTE that we cannot do the comparison as binary fields because maybe the secondary index record has already been updated to a different binary value in a char field, but the collation identifies the old and new value anyway! */ if (entry && !dtuple_coll_cmp(ientry, entry)) { mem_heap_free(heap); return(TRUE); } } version = prev_version; } } /*****************************************************************//** Constructs the version of a clustered index record which a consistent read should see. We assume that the trx id stored in rec is such that the consistent read should not see rec in its present version. @return DB_SUCCESS or DB_MISSING_HISTORY */ UNIV_INTERN dberr_t row_vers_build_for_consistent_read( /*===============================*/ const rec_t* rec, /*!< in: record in a clustered index; the caller must have a latch on the page; this latch locks the top of the stack of versions of this records */ mtr_t* mtr, /*!< in: mtr holding the latch on rec */ dict_index_t* index, /*!< in: the clustered index */ ulint** offsets,/*!< in/out: offsets returned by rec_get_offsets(rec, index) */ read_view_t* view, /*!< in: the consistent read view */ mem_heap_t** offset_heap,/*!< in/out: memory heap from which the offsets are allocated */ mem_heap_t* in_heap,/*!< in: memory heap from which the memory for *old_vers is allocated; memory for possible intermediate versions is allocated and freed locally within the function */ rec_t** old_vers)/*!< out, own: old version, or NULL if the history is missing or the record does not exist in the view, that is, it was freshly inserted afterwards */ { const rec_t* version; rec_t* prev_version; trx_id_t trx_id; mem_heap_t* heap = NULL; byte* buf; dberr_t err; ut_ad(dict_index_is_clust(index)); ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX) || mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_S_FIX)); #ifdef UNIV_SYNC_DEBUG ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED)); #endif /* UNIV_SYNC_DEBUG */ ut_ad(rec_offs_validate(rec, index, *offsets)); trx_id = row_get_rec_trx_id(rec, index, *offsets); ut_ad(!read_view_sees_trx_id(view, trx_id)); version = rec; for (;;) { mem_heap_t* heap2 = heap; trx_undo_rec_t* undo_rec; roll_ptr_t roll_ptr; undo_no_t undo_no; heap = mem_heap_create(1024); /* If we have high-granularity consistent read view and creating transaction of the view is the same as trx_id in the record we see this record only in the case when undo_no of the record is < undo_no in the view. */ if (view->type == VIEW_HIGH_GRANULARITY && view->creator_trx_id == trx_id) { roll_ptr = row_get_rec_roll_ptr(version, index, *offsets); undo_rec = trx_undo_get_undo_rec_low(roll_ptr, heap); undo_no = trx_undo_rec_get_undo_no(undo_rec); mem_heap_empty(heap); if (view->undo_no > undo_no) { /* The view already sees this version: we can copy it to in_heap and return */ #if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG ut_a(!rec_offs_any_null_extern( version, *offsets)); #endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */ buf = static_cast(mem_heap_alloc( in_heap, rec_offs_size(*offsets))); *old_vers = rec_copy(buf, version, *offsets); rec_offs_make_valid(*old_vers, index, *offsets); err = DB_SUCCESS; break; } } err = trx_undo_prev_version_build(rec, mtr, version, index, *offsets, heap, &prev_version) ? DB_SUCCESS : DB_MISSING_HISTORY; if (heap2) { mem_heap_free(heap2); /* free version */ } if (prev_version == NULL) { /* It was a freshly inserted version */ *old_vers = NULL; break; } *offsets = rec_get_offsets(prev_version, index, *offsets, ULINT_UNDEFINED, offset_heap); #if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG ut_a(!rec_offs_any_null_extern(prev_version, *offsets)); #endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */ trx_id = row_get_rec_trx_id(prev_version, index, *offsets); if (read_view_sees_trx_id(view, trx_id)) { /* The view already sees this version: we can copy it to in_heap and return */ buf = static_cast( mem_heap_alloc( in_heap, rec_offs_size(*offsets))); *old_vers = rec_copy(buf, prev_version, *offsets); rec_offs_make_valid(*old_vers, index, *offsets); break; } version = prev_version; }/* for (;;) */ mem_heap_free(heap); return(err); } /*****************************************************************//** Constructs the last committed version of a clustered index record, which should be seen by a semi-consistent read. */ UNIV_INTERN void row_vers_build_for_semi_consistent_read( /*====================================*/ const rec_t* rec, /*!< in: record in a clustered index; the caller must have a latch on the page; this latch locks the top of the stack of versions of this records */ mtr_t* mtr, /*!< in: mtr holding the latch on rec */ dict_index_t* index, /*!< in: the clustered index */ ulint** offsets,/*!< in/out: offsets returned by rec_get_offsets(rec, index) */ mem_heap_t** offset_heap,/*!< in/out: memory heap from which the offsets are allocated */ mem_heap_t* in_heap,/*!< in: memory heap from which the memory for *old_vers is allocated; memory for possible intermediate versions is allocated and freed locally within the function */ const rec_t** old_vers)/*!< out: rec, old version, or NULL if the record does not exist in the view, that is, it was freshly inserted afterwards */ { const rec_t* version; mem_heap_t* heap = NULL; byte* buf; trx_id_t rec_trx_id = 0; ut_ad(dict_index_is_clust(index)); ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX) || mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_S_FIX)); #ifdef UNIV_SYNC_DEBUG ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED)); #endif /* UNIV_SYNC_DEBUG */ ut_ad(rec_offs_validate(rec, index, *offsets)); version = rec; for (;;) { trx_id_t* version_trx_descr; mem_heap_t* heap2; rec_t* prev_version; trx_id_t version_trx_id; version_trx_id = row_get_rec_trx_id(version, index, *offsets); if (rec == version) { rec_trx_id = version_trx_id; } mutex_enter(&trx_sys->mutex); version_trx_descr = trx_find_descriptor(trx_sys->descriptors, trx_sys->descr_n_used, version_trx_id); /* Because version_trx is a read-write transaction, its state cannot change from or to NOT_STARTED while we are holding the trx_sys->mutex. It may change from ACTIVE to PREPARED or COMMITTED. */ mutex_exit(&trx_sys->mutex); if (!version_trx_descr) { committed_version_trx: /* We found a version that belongs to a committed transaction: return it. */ #if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG ut_a(!rec_offs_any_null_extern(version, *offsets)); #endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */ if (rec == version) { *old_vers = rec; break; } /* We assume that a rolled-back transaction stays in TRX_STATE_ACTIVE state until all the changes have been rolled back and the transaction is removed from the global list of transactions. */ if (rec_trx_id == version_trx_id) { /* The transaction was committed while we searched for earlier versions. Return the current version as a semi-consistent read. */ version = rec; *offsets = rec_get_offsets(version, index, *offsets, ULINT_UNDEFINED, offset_heap); } buf = static_cast( mem_heap_alloc( in_heap, rec_offs_size(*offsets))); *old_vers = rec_copy(buf, version, *offsets); rec_offs_make_valid(*old_vers, index, *offsets); break; } DEBUG_SYNC_C("after_row_vers_check_trx_active"); heap2 = heap; heap = mem_heap_create(1024); if (!trx_undo_prev_version_build(rec, mtr, version, index, *offsets, heap, &prev_version)) { mem_heap_free(heap); heap = heap2; heap2 = NULL; goto committed_version_trx; } if (heap2) { mem_heap_free(heap2); /* free version */ } if (prev_version == NULL) { /* It was a freshly inserted version */ *old_vers = NULL; break; } version = prev_version; *offsets = rec_get_offsets(version, index, *offsets, ULINT_UNDEFINED, offset_heap); #if defined UNIV_DEBUG || defined UNIV_BLOB_LIGHT_DEBUG ut_a(!rec_offs_any_null_extern(version, *offsets)); #endif /* UNIV_DEBUG || UNIV_BLOB_LIGHT_DEBUG */ }/* for (;;) */ if (heap) { mem_heap_free(heap); } }