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Until now, only selected bulk operations (e.g. COPY) did this. If a given relfilenode received both a WAL-skipping COPY and a WAL-logged operation (e.g. INSERT), recovery could lose tuples from the COPY. See src/backend/access/transam/README section "Skipping WAL for New RelFileNode" for the new coding rules. Maintainers of table access methods should examine that section. To maintain data durability, just before commit, we choose between an fsync of the relfilenode and copying its contents to WAL. A new GUC, wal_skip_threshold, guides that choice. If this change slows a workload that creates small, permanent relfilenodes under wal_level=minimal, try adjusting wal_skip_threshold. Users setting a timeout on COMMIT may need to adjust that timeout, and log_min_duration_statement analysis will reflect time consumption moving to COMMIT from commands like COPY. Internally, this requires a reliable determination of whether RollbackAndReleaseCurrentSubTransaction() would unlink a relation's current relfilenode. Introduce rd_firstRelfilenodeSubid. Amend the specification of rd_createSubid such that the field is zero when a new rel has an old rd_node. Make relcache.c retain entries for certain dropped relations until end of transaction. Bump XLOG_PAGE_MAGIC, since this introduces XLOG_GIST_ASSIGN_LSN. Future servers accept older WAL, so this bump is discretionary. Kyotaro Horiguchi, reviewed (in earlier, similar versions) by Robert Haas. Heikki Linnakangas and Michael Paquier implemented earlier designs that materially clarified the problem. Reviewed, in earlier designs, by Andrew Dunstan, Andres Freund, Alvaro Herrera, Tom Lane, Fujii Masao, and Simon Riggs. Reported by Martijn van Oosterhout. Discussion: https://postgr.es/m/20150702220524.GA9392@svana.org
58 lines
1.8 KiB
C
58 lines
1.8 KiB
C
/*-------------------------------------------------------------------------
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*
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* rewriteheap.h
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* Declarations for heap rewrite support functions
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*
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* Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994-5, Regents of the University of California
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*
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* src/include/access/rewriteheap.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef REWRITE_HEAP_H
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#define REWRITE_HEAP_H
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#include "access/htup.h"
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#include "storage/itemptr.h"
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#include "storage/relfilenode.h"
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#include "utils/relcache.h"
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/* struct definition is private to rewriteheap.c */
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typedef struct RewriteStateData *RewriteState;
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extern RewriteState begin_heap_rewrite(Relation OldHeap, Relation NewHeap,
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TransactionId OldestXmin, TransactionId FreezeXid,
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MultiXactId MultiXactCutoff);
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extern void end_heap_rewrite(RewriteState state);
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extern void rewrite_heap_tuple(RewriteState state, HeapTuple oldTuple,
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HeapTuple newTuple);
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extern bool rewrite_heap_dead_tuple(RewriteState state, HeapTuple oldTuple);
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/*
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* On-Disk data format for an individual logical rewrite mapping.
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*/
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typedef struct LogicalRewriteMappingData
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{
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RelFileNode old_node;
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RelFileNode new_node;
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ItemPointerData old_tid;
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ItemPointerData new_tid;
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} LogicalRewriteMappingData;
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/* ---
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* The filename consists of the following, dash separated,
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* components:
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* 1) database oid or InvalidOid for shared relations
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* 2) the oid of the relation
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* 3) upper 32bit of the LSN at which a rewrite started
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* 4) lower 32bit of the LSN at which a rewrite started
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* 5) xid we are mapping for
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* 6) xid of the xact performing the mapping
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* ---
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*/
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#define LOGICAL_REWRITE_FORMAT "map-%x-%x-%X_%X-%x-%x"
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void CheckPointLogicalRewriteHeap(void);
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#endif /* REWRITE_HEAP_H */
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