708 lines
20 KiB
C
708 lines
20 KiB
C
/*-------------------------------------------------------------------------
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*
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* storage.c
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* code to create and destroy physical storage for relations
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*
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* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/backend/catalog/storage.c
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*
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* NOTES
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* Some of this code used to be in storage/smgr/smgr.c, and the
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* function names still reflect that.
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/visibilitymap.h"
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#include "access/xact.h"
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#include "access/xlog.h"
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#include "access/xloginsert.h"
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#include "access/xlogutils.h"
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#include "catalog/storage.h"
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#include "catalog/storage_xlog.h"
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#include "miscadmin.h"
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#include "storage/freespace.h"
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#include "storage/smgr.h"
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#include "utils/memutils.h"
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#include "utils/rel.h"
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/*
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* We keep a list of all relations (represented as RelFileNode values)
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* that have been created or deleted in the current transaction. When
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* a relation is created, we create the physical file immediately, but
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* remember it so that we can delete the file again if the current
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* transaction is aborted. Conversely, a deletion request is NOT
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* executed immediately, but is just entered in the list. When and if
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* the transaction commits, we can delete the physical file.
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*
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* To handle subtransactions, every entry is marked with its transaction
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* nesting level. At subtransaction commit, we reassign the subtransaction's
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* entries to the parent nesting level. At subtransaction abort, we can
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* immediately execute the abort-time actions for all entries of the current
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* nesting level.
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*
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* NOTE: the list is kept in TopMemoryContext to be sure it won't disappear
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* unbetimes. It'd probably be OK to keep it in TopTransactionContext,
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* but I'm being paranoid.
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*/
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typedef struct PendingRelDelete
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{
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RelFileNode relnode; /* relation that may need to be deleted */
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BackendId backend; /* InvalidBackendId if not a temp rel */
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bool atCommit; /* T=delete at commit; F=delete at abort */
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int nestLevel; /* xact nesting level of request */
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struct PendingRelDelete *next; /* linked-list link */
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} PendingRelDelete;
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static PendingRelDelete *pendingDeletes = NULL; /* head of linked list */
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/*
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* RelationCreateStorage
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* Create physical storage for a relation.
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*
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* Create the underlying disk file storage for the relation. This only
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* creates the main fork; additional forks are created lazily by the
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* modules that need them.
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*
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* This function is transactional. The creation is WAL-logged, and if the
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* transaction aborts later on, the storage will be destroyed.
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*/
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SMgrRelation
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RelationCreateStorage(RelFileNode rnode, char relpersistence)
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{
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PendingRelDelete *pending;
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SMgrRelation srel;
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BackendId backend;
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bool needs_wal;
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switch (relpersistence)
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{
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case RELPERSISTENCE_TEMP:
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backend = BackendIdForTempRelations();
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needs_wal = false;
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break;
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case RELPERSISTENCE_UNLOGGED:
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backend = InvalidBackendId;
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needs_wal = false;
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break;
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case RELPERSISTENCE_PERMANENT:
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backend = InvalidBackendId;
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needs_wal = true;
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break;
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default:
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elog(ERROR, "invalid relpersistence: %c", relpersistence);
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return NULL; /* placate compiler */
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}
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srel = smgropen(rnode, backend);
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smgrcreate(srel, MAIN_FORKNUM, false);
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if (needs_wal)
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log_smgrcreate(&srel->smgr_rnode.node, MAIN_FORKNUM);
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/* Add the relation to the list of stuff to delete at abort */
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pending = (PendingRelDelete *)
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MemoryContextAlloc(TopMemoryContext, sizeof(PendingRelDelete));
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pending->relnode = rnode;
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pending->backend = backend;
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pending->atCommit = false; /* delete if abort */
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pending->nestLevel = GetCurrentTransactionNestLevel();
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pending->next = pendingDeletes;
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pendingDeletes = pending;
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return srel;
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}
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/*
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* Perform XLogInsert of an XLOG_SMGR_CREATE record to WAL.
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*/
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void
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log_smgrcreate(const RelFileNode *rnode, ForkNumber forkNum)
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{
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xl_smgr_create xlrec;
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/*
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* Make an XLOG entry reporting the file creation.
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*/
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xlrec.rnode = *rnode;
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xlrec.forkNum = forkNum;
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XLogBeginInsert();
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XLogRegisterData((char *) &xlrec, sizeof(xlrec));
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XLogInsert(RM_SMGR_ID, XLOG_SMGR_CREATE | XLR_SPECIAL_REL_UPDATE);
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}
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/*
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* RelationDropStorage
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* Schedule unlinking of physical storage at transaction commit.
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*/
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void
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RelationDropStorage(Relation rel)
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{
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PendingRelDelete *pending;
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/* Add the relation to the list of stuff to delete at commit */
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pending = (PendingRelDelete *)
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MemoryContextAlloc(TopMemoryContext, sizeof(PendingRelDelete));
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pending->relnode = rel->rd_node;
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pending->backend = rel->rd_backend;
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pending->atCommit = true; /* delete if commit */
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pending->nestLevel = GetCurrentTransactionNestLevel();
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pending->next = pendingDeletes;
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pendingDeletes = pending;
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/*
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* NOTE: if the relation was created in this transaction, it will now be
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* present in the pending-delete list twice, once with atCommit true and
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* once with atCommit false. Hence, it will be physically deleted at end
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* of xact in either case (and the other entry will be ignored by
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* smgrDoPendingDeletes, so no error will occur). We could instead remove
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* the existing list entry and delete the physical file immediately, but
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* for now I'll keep the logic simple.
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*/
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RelationCloseSmgr(rel);
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}
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/*
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* RelationPreserveStorage
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* Mark a relation as not to be deleted after all.
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*
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* We need this function because relation mapping changes are committed
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* separately from commit of the whole transaction, so it's still possible
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* for the transaction to abort after the mapping update is done.
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* When a new physical relation is installed in the map, it would be
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* scheduled for delete-on-abort, so we'd delete it, and be in trouble.
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* The relation mapper fixes this by telling us to not delete such relations
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* after all as part of its commit.
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*
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* We also use this to reuse an old build of an index during ALTER TABLE, this
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* time removing the delete-at-commit entry.
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*
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* No-op if the relation is not among those scheduled for deletion.
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*/
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void
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RelationPreserveStorage(RelFileNode rnode, bool atCommit)
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{
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PendingRelDelete *pending;
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PendingRelDelete *prev;
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PendingRelDelete *next;
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prev = NULL;
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for (pending = pendingDeletes; pending != NULL; pending = next)
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{
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next = pending->next;
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if (RelFileNodeEquals(rnode, pending->relnode)
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&& pending->atCommit == atCommit)
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{
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/* unlink and delete list entry */
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if (prev)
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prev->next = next;
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else
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pendingDeletes = next;
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pfree(pending);
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/* prev does not change */
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}
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else
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{
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/* unrelated entry, don't touch it */
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prev = pending;
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}
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}
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}
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/*
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* RelationTruncate
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* Physically truncate a relation to the specified number of blocks.
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*
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* This includes getting rid of any buffers for the blocks that are to be
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* dropped.
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*/
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void
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RelationTruncate(Relation rel, BlockNumber nblocks)
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{
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bool fsm;
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bool vm;
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bool need_fsm_vacuum = false;
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ForkNumber forks[MAX_FORKNUM];
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BlockNumber blocks[MAX_FORKNUM];
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int nforks = 0;
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/* Open it at the smgr level if not already done */
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RelationOpenSmgr(rel);
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/*
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* Make sure smgr_targblock etc aren't pointing somewhere past new end
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*/
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rel->rd_smgr->smgr_targblock = InvalidBlockNumber;
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rel->rd_smgr->smgr_fsm_nblocks = InvalidBlockNumber;
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rel->rd_smgr->smgr_vm_nblocks = InvalidBlockNumber;
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/* Prepare for truncation of MAIN fork of the relation */
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forks[nforks] = MAIN_FORKNUM;
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blocks[nforks] = nblocks;
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nforks++;
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/* Prepare for truncation of the FSM if it exists */
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fsm = smgrexists(rel->rd_smgr, FSM_FORKNUM);
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if (fsm)
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{
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blocks[nforks] = FreeSpaceMapPrepareTruncateRel(rel, nblocks);
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if (BlockNumberIsValid(blocks[nforks]))
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{
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forks[nforks] = FSM_FORKNUM;
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nforks++;
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need_fsm_vacuum = true;
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}
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}
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/* Prepare for truncation of the visibility map too if it exists */
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vm = smgrexists(rel->rd_smgr, VISIBILITYMAP_FORKNUM);
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if (vm)
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{
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blocks[nforks] = visibilitymap_prepare_truncate(rel, nblocks);
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if (BlockNumberIsValid(blocks[nforks]))
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{
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forks[nforks] = VISIBILITYMAP_FORKNUM;
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nforks++;
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}
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}
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/*
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* We WAL-log the truncation before actually truncating, which means
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* trouble if the truncation fails. If we then crash, the WAL replay
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* likely isn't going to succeed in the truncation either, and cause a
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* PANIC. It's tempting to put a critical section here, but that cure
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* would be worse than the disease. It would turn a usually harmless
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* failure to truncate, that might spell trouble at WAL replay, into a
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* certain PANIC.
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*/
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if (RelationNeedsWAL(rel))
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{
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/*
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* Make an XLOG entry reporting the file truncation.
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*/
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XLogRecPtr lsn;
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xl_smgr_truncate xlrec;
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xlrec.blkno = nblocks;
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xlrec.rnode = rel->rd_node;
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xlrec.flags = SMGR_TRUNCATE_ALL;
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XLogBeginInsert();
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XLogRegisterData((char *) &xlrec, sizeof(xlrec));
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lsn = XLogInsert(RM_SMGR_ID,
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XLOG_SMGR_TRUNCATE | XLR_SPECIAL_REL_UPDATE);
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/*
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* Flush, because otherwise the truncation of the main relation might
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* hit the disk before the WAL record, and the truncation of the FSM
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* or visibility map. If we crashed during that window, we'd be left
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* with a truncated heap, but the FSM or visibility map would still
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* contain entries for the non-existent heap pages.
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*/
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if (fsm || vm)
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XLogFlush(lsn);
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}
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/* Do the real work to truncate relation forks */
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smgrtruncate(rel->rd_smgr, forks, nforks, blocks);
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/*
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* Update upper-level FSM pages to account for the truncation.
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* This is important because the just-truncated pages were likely
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* marked as all-free, and would be preferentially selected.
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*/
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if (need_fsm_vacuum)
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FreeSpaceMapVacuumRange(rel, nblocks, InvalidBlockNumber);
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}
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/*
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* Copy a fork's data, block by block.
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*
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* Note that this requires that there is no dirty data in shared buffers. If
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* it's possible that there are, callers need to flush those using
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* e.g. FlushRelationBuffers(rel).
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*/
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void
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RelationCopyStorage(SMgrRelation src, SMgrRelation dst,
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ForkNumber forkNum, char relpersistence)
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{
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PGAlignedBlock buf;
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Page page;
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bool use_wal;
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bool copying_initfork;
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BlockNumber nblocks;
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BlockNumber blkno;
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page = (Page) buf.data;
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/*
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* The init fork for an unlogged relation in many respects has to be
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* treated the same as normal relation, changes need to be WAL logged and
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* it needs to be synced to disk.
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*/
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copying_initfork = relpersistence == RELPERSISTENCE_UNLOGGED &&
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forkNum == INIT_FORKNUM;
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/*
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* We need to log the copied data in WAL iff WAL archiving/streaming is
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* enabled AND it's a permanent relation.
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*/
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use_wal = XLogIsNeeded() &&
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(relpersistence == RELPERSISTENCE_PERMANENT || copying_initfork);
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nblocks = smgrnblocks(src, forkNum);
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for (blkno = 0; blkno < nblocks; blkno++)
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{
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/* If we got a cancel signal during the copy of the data, quit */
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CHECK_FOR_INTERRUPTS();
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smgrread(src, forkNum, blkno, buf.data);
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if (!PageIsVerified(page, blkno))
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ereport(ERROR,
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(errcode(ERRCODE_DATA_CORRUPTED),
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errmsg("invalid page in block %u of relation %s",
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blkno,
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relpathbackend(src->smgr_rnode.node,
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src->smgr_rnode.backend,
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forkNum))));
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/*
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* WAL-log the copied page. Unfortunately we don't know what kind of a
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* page this is, so we have to log the full page including any unused
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* space.
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*/
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if (use_wal)
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log_newpage(&dst->smgr_rnode.node, forkNum, blkno, page, false);
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PageSetChecksumInplace(page, blkno);
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/*
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* Now write the page. We say skipFsync = true because there's no
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* need for smgr to schedule an fsync for this write; we'll do it
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* ourselves below.
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*/
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smgrextend(dst, forkNum, blkno, buf.data, true);
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}
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/*
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* If the rel is WAL-logged, must fsync before commit. We use heap_sync
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* to ensure that the toast table gets fsync'd too. (For a temp or
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* unlogged rel we don't care since the data will be gone after a crash
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* anyway.)
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*
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* It's obvious that we must do this when not WAL-logging the copy. It's
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* less obvious that we have to do it even if we did WAL-log the copied
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* pages. The reason is that since we're copying outside shared buffers, a
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* CHECKPOINT occurring during the copy has no way to flush the previously
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* written data to disk (indeed it won't know the new rel even exists). A
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* crash later on would replay WAL from the checkpoint, therefore it
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* wouldn't replay our earlier WAL entries. If we do not fsync those pages
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* here, they might still not be on disk when the crash occurs.
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*/
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if (relpersistence == RELPERSISTENCE_PERMANENT || copying_initfork)
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smgrimmedsync(dst, forkNum);
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}
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/*
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* smgrDoPendingDeletes() -- Take care of relation deletes at end of xact.
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*
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* This also runs when aborting a subxact; we want to clean up a failed
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* subxact immediately.
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*
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* Note: It's possible that we're being asked to remove a relation that has
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* no physical storage in any fork. In particular, it's possible that we're
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* cleaning up an old temporary relation for which RemovePgTempFiles has
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* already recovered the physical storage.
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*/
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void
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smgrDoPendingDeletes(bool isCommit)
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{
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int nestLevel = GetCurrentTransactionNestLevel();
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PendingRelDelete *pending;
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PendingRelDelete *prev;
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PendingRelDelete *next;
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int nrels = 0,
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i = 0,
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maxrels = 0;
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SMgrRelation *srels = NULL;
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prev = NULL;
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for (pending = pendingDeletes; pending != NULL; pending = next)
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{
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next = pending->next;
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if (pending->nestLevel < nestLevel)
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{
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/* outer-level entries should not be processed yet */
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prev = pending;
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}
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else
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{
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/* unlink list entry first, so we don't retry on failure */
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if (prev)
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prev->next = next;
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else
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pendingDeletes = next;
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/* do deletion if called for */
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if (pending->atCommit == isCommit)
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{
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SMgrRelation srel;
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srel = smgropen(pending->relnode, pending->backend);
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/* allocate the initial array, or extend it, if needed */
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if (maxrels == 0)
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{
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maxrels = 8;
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srels = palloc(sizeof(SMgrRelation) * maxrels);
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}
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else if (maxrels <= nrels)
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{
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maxrels *= 2;
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srels = repalloc(srels, sizeof(SMgrRelation) * maxrels);
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}
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srels[nrels++] = srel;
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}
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/* must explicitly free the list entry */
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pfree(pending);
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/* prev does not change */
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}
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}
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if (nrels > 0)
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{
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smgrdounlinkall(srels, nrels, false);
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for (i = 0; i < nrels; i++)
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smgrclose(srels[i]);
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pfree(srels);
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}
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}
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/*
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* smgrGetPendingDeletes() -- Get a list of non-temp relations to be deleted.
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*
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* The return value is the number of relations scheduled for termination.
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* *ptr is set to point to a freshly-palloc'd array of RelFileNodes.
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* If there are no relations to be deleted, *ptr is set to NULL.
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*
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* Only non-temporary relations are included in the returned list. This is OK
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* because the list is used only in contexts where temporary relations don't
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* matter: we're either writing to the two-phase state file (and transactions
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* that have touched temp tables can't be prepared) or we're writing to xlog
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* (and all temporary files will be zapped if we restart anyway, so no need
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* for redo to do it also).
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*
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* Note that the list does not include anything scheduled for termination
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* by upper-level transactions.
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*/
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int
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smgrGetPendingDeletes(bool forCommit, RelFileNode **ptr)
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{
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int nestLevel = GetCurrentTransactionNestLevel();
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int nrels;
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RelFileNode *rptr;
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PendingRelDelete *pending;
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nrels = 0;
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for (pending = pendingDeletes; pending != NULL; pending = pending->next)
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{
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if (pending->nestLevel >= nestLevel && pending->atCommit == forCommit
|
|
&& pending->backend == InvalidBackendId)
|
|
nrels++;
|
|
}
|
|
if (nrels == 0)
|
|
{
|
|
*ptr = NULL;
|
|
return 0;
|
|
}
|
|
rptr = (RelFileNode *) palloc(nrels * sizeof(RelFileNode));
|
|
*ptr = rptr;
|
|
for (pending = pendingDeletes; pending != NULL; pending = pending->next)
|
|
{
|
|
if (pending->nestLevel >= nestLevel && pending->atCommit == forCommit
|
|
&& pending->backend == InvalidBackendId)
|
|
{
|
|
*rptr = pending->relnode;
|
|
rptr++;
|
|
}
|
|
}
|
|
return nrels;
|
|
}
|
|
|
|
/*
|
|
* PostPrepare_smgr -- Clean up after a successful PREPARE
|
|
*
|
|
* What we have to do here is throw away the in-memory state about pending
|
|
* relation deletes. It's all been recorded in the 2PC state file and
|
|
* it's no longer smgr's job to worry about it.
|
|
*/
|
|
void
|
|
PostPrepare_smgr(void)
|
|
{
|
|
PendingRelDelete *pending;
|
|
PendingRelDelete *next;
|
|
|
|
for (pending = pendingDeletes; pending != NULL; pending = next)
|
|
{
|
|
next = pending->next;
|
|
pendingDeletes = next;
|
|
/* must explicitly free the list entry */
|
|
pfree(pending);
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* AtSubCommit_smgr() --- Take care of subtransaction commit.
|
|
*
|
|
* Reassign all items in the pending-deletes list to the parent transaction.
|
|
*/
|
|
void
|
|
AtSubCommit_smgr(void)
|
|
{
|
|
int nestLevel = GetCurrentTransactionNestLevel();
|
|
PendingRelDelete *pending;
|
|
|
|
for (pending = pendingDeletes; pending != NULL; pending = pending->next)
|
|
{
|
|
if (pending->nestLevel >= nestLevel)
|
|
pending->nestLevel = nestLevel - 1;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* AtSubAbort_smgr() --- Take care of subtransaction abort.
|
|
*
|
|
* Delete created relations and forget about deleted relations.
|
|
* We can execute these operations immediately because we know this
|
|
* subtransaction will not commit.
|
|
*/
|
|
void
|
|
AtSubAbort_smgr(void)
|
|
{
|
|
smgrDoPendingDeletes(false);
|
|
}
|
|
|
|
void
|
|
smgr_redo(XLogReaderState *record)
|
|
{
|
|
XLogRecPtr lsn = record->EndRecPtr;
|
|
uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
|
|
|
|
/* Backup blocks are not used in smgr records */
|
|
Assert(!XLogRecHasAnyBlockRefs(record));
|
|
|
|
if (info == XLOG_SMGR_CREATE)
|
|
{
|
|
xl_smgr_create *xlrec = (xl_smgr_create *) XLogRecGetData(record);
|
|
SMgrRelation reln;
|
|
|
|
reln = smgropen(xlrec->rnode, InvalidBackendId);
|
|
smgrcreate(reln, xlrec->forkNum, true);
|
|
}
|
|
else if (info == XLOG_SMGR_TRUNCATE)
|
|
{
|
|
xl_smgr_truncate *xlrec = (xl_smgr_truncate *) XLogRecGetData(record);
|
|
SMgrRelation reln;
|
|
Relation rel;
|
|
ForkNumber forks[MAX_FORKNUM];
|
|
BlockNumber blocks[MAX_FORKNUM];
|
|
int nforks = 0;
|
|
bool need_fsm_vacuum = false;
|
|
|
|
reln = smgropen(xlrec->rnode, InvalidBackendId);
|
|
|
|
/*
|
|
* Forcibly create relation if it doesn't exist (which suggests that
|
|
* it was dropped somewhere later in the WAL sequence). As in
|
|
* XLogReadBufferForRedo, we prefer to recreate the rel and replay the
|
|
* log as best we can until the drop is seen.
|
|
*/
|
|
smgrcreate(reln, MAIN_FORKNUM, true);
|
|
|
|
/*
|
|
* Before we perform the truncation, update minimum recovery point to
|
|
* cover this WAL record. Once the relation is truncated, there's no
|
|
* going back. The buffer manager enforces the WAL-first rule for
|
|
* normal updates to relation files, so that the minimum recovery
|
|
* point is always updated before the corresponding change in the data
|
|
* file is flushed to disk. We have to do the same manually here.
|
|
*
|
|
* Doing this before the truncation means that if the truncation fails
|
|
* for some reason, you cannot start up the system even after restart,
|
|
* until you fix the underlying situation so that the truncation will
|
|
* succeed. Alternatively, we could update the minimum recovery point
|
|
* after truncation, but that would leave a small window where the
|
|
* WAL-first rule could be violated.
|
|
*/
|
|
XLogFlush(lsn);
|
|
|
|
/* Prepare for truncation of MAIN fork */
|
|
if ((xlrec->flags & SMGR_TRUNCATE_HEAP) != 0)
|
|
{
|
|
forks[nforks] = MAIN_FORKNUM;
|
|
blocks[nforks] = xlrec->blkno;
|
|
nforks++;
|
|
|
|
/* Also tell xlogutils.c about it */
|
|
XLogTruncateRelation(xlrec->rnode, MAIN_FORKNUM, xlrec->blkno);
|
|
}
|
|
|
|
/* Prepare for truncation of FSM and VM too */
|
|
rel = CreateFakeRelcacheEntry(xlrec->rnode);
|
|
|
|
if ((xlrec->flags & SMGR_TRUNCATE_FSM) != 0 &&
|
|
smgrexists(reln, FSM_FORKNUM))
|
|
{
|
|
blocks[nforks] = FreeSpaceMapPrepareTruncateRel(rel, xlrec->blkno);
|
|
if (BlockNumberIsValid(blocks[nforks]))
|
|
{
|
|
forks[nforks] = FSM_FORKNUM;
|
|
nforks++;
|
|
need_fsm_vacuum = true;
|
|
}
|
|
}
|
|
if ((xlrec->flags & SMGR_TRUNCATE_VM) != 0 &&
|
|
smgrexists(reln, VISIBILITYMAP_FORKNUM))
|
|
{
|
|
blocks[nforks] = visibilitymap_prepare_truncate(rel, xlrec->blkno);
|
|
if (BlockNumberIsValid(blocks[nforks]))
|
|
{
|
|
forks[nforks] = VISIBILITYMAP_FORKNUM;
|
|
nforks++;
|
|
}
|
|
}
|
|
|
|
/* Do the real work to truncate relation forks */
|
|
if (nforks > 0)
|
|
smgrtruncate(reln, forks, nforks, blocks);
|
|
|
|
/*
|
|
* Update upper-level FSM pages to account for the truncation.
|
|
* This is important because the just-truncated pages were likely
|
|
* marked as all-free, and would be preferentially selected.
|
|
*/
|
|
if (need_fsm_vacuum)
|
|
FreeSpaceMapVacuumRange(rel, xlrec->blkno,
|
|
InvalidBlockNumber);
|
|
|
|
FreeFakeRelcacheEntry(rel);
|
|
}
|
|
else
|
|
elog(PANIC, "smgr_redo: unknown op code %u", info);
|
|
}
|