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556 lines
15 KiB
C
556 lines
15 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) 1996-2011, 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/xlogutils.h"
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#include "catalog/catalog.h"
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#include "catalog/storage.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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* Declarations for smgr-related XLOG records
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*
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* Note: we log file creation and truncation here, but logging of deletion
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* actions is handled by xact.c, because it is part of transaction commit.
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*/
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/* XLOG gives us high 4 bits */
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#define XLOG_SMGR_CREATE 0x10
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#define XLOG_SMGR_TRUNCATE 0x20
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typedef struct xl_smgr_create
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{
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RelFileNode rnode;
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ForkNumber forkNum;
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} xl_smgr_create;
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typedef struct xl_smgr_truncate
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{
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BlockNumber blkno;
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RelFileNode rnode;
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} xl_smgr_truncate;
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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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void
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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 = MyBackendId;
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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; /* 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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}
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/*
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* Perform XLogInsert of a XLOG_SMGR_CREATE record to WAL.
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*/
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void
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log_smgrcreate(RelFileNode *rnode, ForkNumber forkNum)
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{
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xl_smgr_create xlrec;
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XLogRecData rdata;
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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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rdata.data = (char *) &xlrec;
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rdata.len = sizeof(xlrec);
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rdata.buffer = InvalidBuffer;
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rdata.next = NULL;
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XLogInsert(RM_SMGR_ID, XLOG_SMGR_CREATE, &rdata);
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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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* 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)
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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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{
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/* we should only find delete-on-abort entries, else trouble */
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if (pending->atCommit)
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elog(ERROR, "cannot preserve a delete-on-commit relation");
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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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/* 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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/* Truncate the FSM first if it exists */
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fsm = smgrexists(rel->rd_smgr, FSM_FORKNUM);
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if (fsm)
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FreeSpaceMapTruncateRel(rel, nblocks);
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/* Truncate 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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visibilitymap_truncate(rel, nblocks);
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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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XLogRecData rdata;
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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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rdata.data = (char *) &xlrec;
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rdata.len = sizeof(xlrec);
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rdata.buffer = InvalidBuffer;
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rdata.next = NULL;
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lsn = XLogInsert(RM_SMGR_ID, XLOG_SMGR_TRUNCATE, &rdata);
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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 */
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smgrtruncate(rel->rd_smgr, MAIN_FORKNUM, nblocks);
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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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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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int i;
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srel = smgropen(pending->relnode, pending->backend);
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for (i = 0; i <= MAX_FORKNUM; i++)
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{
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if (smgrexists(srel, i))
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smgrdounlink(srel, i, false);
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}
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smgrclose(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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}
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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
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&& pending->backend == InvalidBackendId)
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nrels++;
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}
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if (nrels == 0)
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{
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*ptr = NULL;
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return 0;
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}
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rptr = (RelFileNode *) palloc(nrels * sizeof(RelFileNode));
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*ptr = rptr;
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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
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&& pending->backend == InvalidBackendId)
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{
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*rptr = pending->relnode;
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rptr++;
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}
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}
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return nrels;
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}
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/*
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* PostPrepare_smgr -- Clean up after a successful PREPARE
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*
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* What we have to do here is throw away the in-memory state about pending
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* relation deletes. It's all been recorded in the 2PC state file and
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* it's no longer smgr's job to worry about it.
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*/
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void
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PostPrepare_smgr(void)
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{
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PendingRelDelete *pending;
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PendingRelDelete *next;
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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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pendingDeletes = next;
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/* must explicitly free the list entry */
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pfree(pending);
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}
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}
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/*
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* AtSubCommit_smgr() --- Take care of subtransaction commit.
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*
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* Reassign all items in the pending-deletes list to the parent transaction.
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*/
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void
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AtSubCommit_smgr(void)
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{
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int nestLevel = GetCurrentTransactionNestLevel();
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PendingRelDelete *pending;
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for (pending = pendingDeletes; pending != NULL; pending = pending->next)
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{
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if (pending->nestLevel >= nestLevel)
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pending->nestLevel = nestLevel - 1;
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}
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}
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/*
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* AtSubAbort_smgr() --- Take care of subtransaction abort.
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*
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* Delete created relations and forget about deleted relations.
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* We can execute these operations immediately because we know this
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* subtransaction will not commit.
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*/
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void
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AtSubAbort_smgr(void)
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{
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smgrDoPendingDeletes(false);
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}
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void
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smgr_redo(XLogRecPtr lsn, XLogRecord *record)
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{
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uint8 info = record->xl_info & ~XLR_INFO_MASK;
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/* Backup blocks are not used in smgr records */
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Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK));
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if (info == XLOG_SMGR_CREATE)
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{
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xl_smgr_create *xlrec = (xl_smgr_create *) XLogRecGetData(record);
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SMgrRelation reln;
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reln = smgropen(xlrec->rnode, InvalidBackendId);
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smgrcreate(reln, xlrec->forkNum, true);
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}
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else if (info == XLOG_SMGR_TRUNCATE)
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{
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xl_smgr_truncate *xlrec = (xl_smgr_truncate *) XLogRecGetData(record);
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SMgrRelation reln;
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Relation rel;
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reln = smgropen(xlrec->rnode, InvalidBackendId);
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/*
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* Forcibly create relation if it doesn't exist (which suggests that
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* it was dropped somewhere later in the WAL sequence). As in
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* XLogOpenRelation, we prefer to recreate the rel and replay the log
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* as best we can until the drop is seen.
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*/
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smgrcreate(reln, MAIN_FORKNUM, true);
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smgrtruncate(reln, MAIN_FORKNUM, xlrec->blkno);
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/* Also tell xlogutils.c about it */
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XLogTruncateRelation(xlrec->rnode, MAIN_FORKNUM, xlrec->blkno);
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/* Truncate FSM and VM too */
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rel = CreateFakeRelcacheEntry(xlrec->rnode);
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if (smgrexists(reln, FSM_FORKNUM))
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FreeSpaceMapTruncateRel(rel, xlrec->blkno);
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if (smgrexists(reln, VISIBILITYMAP_FORKNUM))
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visibilitymap_truncate(rel, xlrec->blkno);
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FreeFakeRelcacheEntry(rel);
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}
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else
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elog(PANIC, "smgr_redo: unknown op code %u", info);
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}
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void
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smgr_desc(StringInfo buf, uint8 xl_info, char *rec)
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{
|
|
uint8 info = xl_info & ~XLR_INFO_MASK;
|
|
|
|
if (info == XLOG_SMGR_CREATE)
|
|
{
|
|
xl_smgr_create *xlrec = (xl_smgr_create *) rec;
|
|
char *path = relpathperm(xlrec->rnode, xlrec->forkNum);
|
|
|
|
appendStringInfo(buf, "file create: %s", path);
|
|
pfree(path);
|
|
}
|
|
else if (info == XLOG_SMGR_TRUNCATE)
|
|
{
|
|
xl_smgr_truncate *xlrec = (xl_smgr_truncate *) rec;
|
|
char *path = relpathperm(xlrec->rnode, MAIN_FORKNUM);
|
|
|
|
appendStringInfo(buf, "file truncate: %s to %u blocks", path,
|
|
xlrec->blkno);
|
|
pfree(path);
|
|
}
|
|
else
|
|
appendStringInfo(buf, "UNKNOWN");
|
|
}
|