On 22/10/15 03:56, Michael Paquier wrote:
On Wed, Oct 21, 2015 at 11:53 PM, Alvaro Herrera
<alvhe...@2ndquadrant.com> wrote:
Heikki Linnakangas wrote:
Thanks. For comparison, I wrote a patch to implement what I had in mind.
When a WAL-skipping COPY begins, we add an entry for that relation in a
"pending-fsyncs" hash table. Whenever we perform any action on a heap that
would normally be WAL-logged, we check if the relation is in the hash table,
and skip WAL-logging if so.
I think this wasn't applied, was it?
No, it was not applied.
I dropped the ball on this one back in July, so here's an attempt to
revive this thread.
I spent some time fixing the remaining issues with the prototype patch I
posted earlier, and rebased that on top of current git master. See attached.
Some review of that would be nice. If there are no major issues with it,
I'm going to create backpatchable versions of this for 9.4 and below.
- Heikki
>From 063e1aa258800873783190a9678d551b43c0e39e Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakan...@iki.fi>
Date: Thu, 4 Feb 2016 15:21:09 +0300
Subject: [PATCH 1/1] Fix the optimization to skip WAL-logging on table created
in same xact.
There were several bugs in the optimization to skip WAL-logging for a table
that was created (or truncated) in the same transaction, with
wal_level=minimal, leading to data loss if a crash happened after the
optimization was used:
* If the table was created, and then truncated, and then loaded with COPY,
we would replay the truncate record at commit, and the table would end
up being empty after replay.
* If there is a trigger on a table that modifies the same table, and you
COPY to the table in the transaction that created it, you might have some
WAL-logged operations on a page, performed by the trigger, intermixed with
the non-WAL-logged inserts done by the COPY. That can lead to crash at
recovery, because we might try to replay a WAL record that e.g. updates
a tuple, but insertion of the tuple was not WAL-logged.
---
src/backend/access/heap/heapam.c | 254 +++++++++++++++++++++++---------
src/backend/access/heap/pruneheap.c | 2 +-
src/backend/access/heap/rewriteheap.c | 4 +-
src/backend/access/heap/visibilitymap.c | 2 +-
src/backend/access/transam/xact.c | 7 +
src/backend/catalog/storage.c | 250 ++++++++++++++++++++++++++++---
src/backend/commands/copy.c | 14 +-
src/backend/commands/createas.c | 9 +-
src/backend/commands/matview.c | 6 +-
src/backend/commands/tablecmds.c | 5 +-
src/backend/commands/vacuumlazy.c | 6 +-
src/backend/storage/buffer/bufmgr.c | 47 ++++--
src/include/access/heapam.h | 8 +-
src/include/access/heapam_xlog.h | 2 +
src/include/catalog/storage.h | 3 +
src/include/storage/bufmgr.h | 2 +
16 files changed, 487 insertions(+), 134 deletions(-)
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index f443742..79298e2 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -34,6 +34,28 @@
* the POSTGRES heap access method used for all POSTGRES
* relations.
*
+ * WAL CONSIDERATIONS
+ * All heap operations are normally WAL-logged. but there are a few
+ * exceptions. Temporary and unlogged relations never need to be
+ * WAL-logged, but we can also skip WAL-logging for a table that was
+ * created in the same transaction, if we don't need WAL for PITR or
+ * WAL archival purposes (i.e. if wal_level=minimal), and we fsync()
+ * the file to disk at COMMIT instead.
+ *
+ * The same-relation optimization is not employed automatically on all
+ * updates to a table that was created in the same transacton, because
+ * for a small number of changes, it's cheaper to just create the WAL
+ * records than fsyncing() the whole relation at COMMIT. It is only
+ * worthwhile for (presumably) large operations like COPY, CLUSTER,
+ * or VACUUM FULL. Use heap_register_sync() to initiate such an
+ * operation; it will cause any subsequent updates to the table to skip
+ * WAL-logging, if possible, and cause the heap to be synced to disk at
+ * COMMIT.
+ *
+ * To make that work, all modifications to heap must use
+ * HeapNeedsWAL() to check if WAL-logging is needed in this transaction
+ * for the given block.
+ *
*-------------------------------------------------------------------------
*/
#include "postgres.h"
@@ -55,6 +77,7 @@
#include "access/xlogutils.h"
#include "catalog/catalog.h"
#include "catalog/namespace.h"
+#include "catalog/storage.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/bufmgr.h"
@@ -2332,12 +2355,6 @@ FreeBulkInsertState(BulkInsertState bistate)
* The new tuple is stamped with current transaction ID and the specified
* command ID.
*
- * If the HEAP_INSERT_SKIP_WAL option is specified, the new tuple is not
- * logged in WAL, even for a non-temp relation. Safe usage of this behavior
- * requires that we arrange that all new tuples go into new pages not
- * containing any tuples from other transactions, and that the relation gets
- * fsync'd before commit. (See also heap_sync() comments)
- *
* The HEAP_INSERT_SKIP_FSM option is passed directly to
* RelationGetBufferForTuple, which see for more info.
*
@@ -2441,7 +2458,7 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
MarkBufferDirty(buffer);
/* XLOG stuff */
- if (!(options & HEAP_INSERT_SKIP_WAL) && RelationNeedsWAL(relation))
+ if (HeapNeedsWAL(relation, buffer))
{
xl_heap_insert xlrec;
xl_heap_header xlhdr;
@@ -2640,12 +2657,10 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
int ndone;
char *scratch = NULL;
Page page;
- bool needwal;
Size saveFreeSpace;
bool need_tuple_data = RelationIsLogicallyLogged(relation);
bool need_cids = RelationIsAccessibleInLogicalDecoding(relation);
- needwal = !(options & HEAP_INSERT_SKIP_WAL) && RelationNeedsWAL(relation);
saveFreeSpace = RelationGetTargetPageFreeSpace(relation,
HEAP_DEFAULT_FILLFACTOR);
@@ -2660,7 +2675,7 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
* palloc() within a critical section is not safe, so we allocate this
* beforehand.
*/
- if (needwal)
+ if (RelationNeedsWAL(relation))
scratch = palloc(BLCKSZ);
/*
@@ -2695,6 +2710,7 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
Buffer vmbuffer = InvalidBuffer;
bool all_visible_cleared = false;
int nthispage;
+ bool needwal;
CHECK_FOR_INTERRUPTS();
@@ -2706,6 +2722,7 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
InvalidBuffer, options, bistate,
&vmbuffer, NULL);
page = BufferGetPage(buffer);
+ needwal = HeapNeedsWAL(relation, buffer);
/* NO EREPORT(ERROR) from here till changes are logged */
START_CRIT_SECTION();
@@ -3262,7 +3279,7 @@ l1:
* NB: heap_abort_speculative() uses the same xlog record and replay
* routines.
*/
- if (RelationNeedsWAL(relation))
+ if (HeapNeedsWAL(relation, buffer))
{
xl_heap_delete xlrec;
XLogRecPtr recptr;
@@ -4130,7 +4147,8 @@ l2:
MarkBufferDirty(buffer);
/* XLOG stuff */
- if (RelationNeedsWAL(relation))
+ if (HeapNeedsWAL(relation, buffer) ||
+ HeapNeedsWAL(relation, newbuf))
{
XLogRecPtr recptr;
@@ -5048,7 +5066,7 @@ failed:
* (Also, in a PITR log-shipping or 2PC environment, we have to have XLOG
* entries for everything anyway.)
*/
- if (RelationNeedsWAL(relation))
+ if (HeapNeedsWAL(relation, *buffer))
{
xl_heap_lock xlrec;
XLogRecPtr recptr;
@@ -5691,7 +5709,7 @@ l4:
MarkBufferDirty(buf);
/* XLOG stuff */
- if (RelationNeedsWAL(rel))
+ if (HeapNeedsWAL(rel, buf))
{
xl_heap_lock_updated xlrec;
XLogRecPtr recptr;
@@ -5831,7 +5849,7 @@ heap_finish_speculative(Relation relation, HeapTuple tuple)
htup->t_ctid = tuple->t_self;
/* XLOG stuff */
- if (RelationNeedsWAL(relation))
+ if (HeapNeedsWAL(relation, buffer))
{
xl_heap_confirm xlrec;
XLogRecPtr recptr;
@@ -5963,7 +5981,7 @@ heap_abort_speculative(Relation relation, HeapTuple tuple)
* The WAL records generated here match heap_delete(). The same recovery
* routines are used.
*/
- if (RelationNeedsWAL(relation))
+ if (HeapNeedsWAL(relation, buffer))
{
xl_heap_delete xlrec;
XLogRecPtr recptr;
@@ -6069,7 +6087,7 @@ heap_inplace_update(Relation relation, HeapTuple tuple)
MarkBufferDirty(buffer);
/* XLOG stuff */
- if (RelationNeedsWAL(relation))
+ if (HeapNeedsWAL(relation, buffer))
{
xl_heap_inplace xlrec;
XLogRecPtr recptr;
@@ -7122,7 +7140,7 @@ log_heap_clean(Relation reln, Buffer buffer,
XLogRecPtr recptr;
/* Caller should not call me on a non-WAL-logged relation */
- Assert(RelationNeedsWAL(reln));
+ Assert(HeapNeedsWAL(reln, buffer));
xlrec.latestRemovedXid = latestRemovedXid;
xlrec.nredirected = nredirected;
@@ -7170,7 +7188,7 @@ log_heap_freeze(Relation reln, Buffer buffer, TransactionId cutoff_xid,
XLogRecPtr recptr;
/* Caller should not call me on a non-WAL-logged relation */
- Assert(RelationNeedsWAL(reln));
+ Assert(HeapNeedsWAL(reln, buffer));
/* nor when there are no tuples to freeze */
Assert(ntuples > 0);
@@ -7254,7 +7272,7 @@ log_heap_update(Relation reln, Buffer oldbuf,
int bufflags;
/* Caller should not call me on a non-WAL-logged relation */
- Assert(RelationNeedsWAL(reln));
+ Assert(HeapNeedsWAL(reln, newbuf) || HeapNeedsWAL(reln, oldbuf));
XLogBeginInsert();
@@ -7357,76 +7375,86 @@ log_heap_update(Relation reln, Buffer oldbuf,
xlrec.new_offnum = ItemPointerGetOffsetNumber(&newtup->t_self);
xlrec.new_xmax = HeapTupleHeaderGetRawXmax(newtup->t_data);
+ XLogRegisterData((char *) &xlrec, SizeOfHeapUpdate);
+
bufflags = REGBUF_STANDARD;
if (init)
bufflags |= REGBUF_WILL_INIT;
if (need_tuple_data)
bufflags |= REGBUF_KEEP_DATA;
- XLogRegisterBuffer(0, newbuf, bufflags);
- if (oldbuf != newbuf)
- XLogRegisterBuffer(1, oldbuf, REGBUF_STANDARD);
-
- XLogRegisterData((char *) &xlrec, SizeOfHeapUpdate);
-
/*
* Prepare WAL data for the new tuple.
*/
- if (prefixlen > 0 || suffixlen > 0)
+ if (HeapNeedsWAL(reln, newbuf))
{
- if (prefixlen > 0 && suffixlen > 0)
- {
- prefix_suffix[0] = prefixlen;
- prefix_suffix[1] = suffixlen;
- XLogRegisterBufData(0, (char *) &prefix_suffix, sizeof(uint16) * 2);
- }
- else if (prefixlen > 0)
- {
- XLogRegisterBufData(0, (char *) &prefixlen, sizeof(uint16));
- }
- else
+ XLogRegisterBuffer(0, newbuf, bufflags);
+
+ if ((prefixlen > 0 || suffixlen > 0))
{
- XLogRegisterBufData(0, (char *) &suffixlen, sizeof(uint16));
+ if (prefixlen > 0 && suffixlen > 0)
+ {
+ prefix_suffix[0] = prefixlen;
+ prefix_suffix[1] = suffixlen;
+ XLogRegisterBufData(0, (char *) &prefix_suffix,
+ sizeof(uint16) * 2);
+ }
+ else if (prefixlen > 0)
+ {
+ XLogRegisterBufData(0, (char *) &prefixlen, sizeof(uint16));
+ }
+ else
+ {
+ XLogRegisterBufData(0, (char *) &suffixlen, sizeof(uint16));
+ }
}
- }
- xlhdr.t_infomask2 = newtup->t_data->t_infomask2;
- xlhdr.t_infomask = newtup->t_data->t_infomask;
- xlhdr.t_hoff = newtup->t_data->t_hoff;
- Assert(SizeofHeapTupleHeader + prefixlen + suffixlen <= newtup->t_len);
+ xlhdr.t_infomask2 = newtup->t_data->t_infomask2;
+ xlhdr.t_infomask = newtup->t_data->t_infomask;
+ xlhdr.t_hoff = newtup->t_data->t_hoff;
+ Assert(SizeofHeapTupleHeader + prefixlen + suffixlen <= newtup->t_len);
- /*
- * PG73FORMAT: write bitmap [+ padding] [+ oid] + data
- *
- * The 'data' doesn't include the common prefix or suffix.
- */
- XLogRegisterBufData(0, (char *) &xlhdr, SizeOfHeapHeader);
- if (prefixlen == 0)
- {
- XLogRegisterBufData(0,
- ((char *) newtup->t_data) + SizeofHeapTupleHeader,
- newtup->t_len - SizeofHeapTupleHeader - suffixlen);
- }
- else
- {
/*
- * Have to write the null bitmap and data after the common prefix as
- * two separate rdata entries.
+ * PG73FORMAT: write bitmap [+ padding] [+ oid] + data
+ *
+ * The 'data' doesn't include the common prefix or suffix.
*/
- /* bitmap [+ padding] [+ oid] */
- if (newtup->t_data->t_hoff - SizeofHeapTupleHeader > 0)
+ XLogRegisterBufData(0, (char *) &xlhdr, SizeOfHeapHeader);
+ if (prefixlen == 0)
{
XLogRegisterBufData(0,
((char *) newtup->t_data) + SizeofHeapTupleHeader,
- newtup->t_data->t_hoff - SizeofHeapTupleHeader);
+ newtup->t_len - SizeofHeapTupleHeader - suffixlen);
}
+ else
+ {
+ /*
+ * Have to write the null bitmap and data after the common prefix
+ * as two separate rdata entries.
+ */
+ /* bitmap [+ padding] [+ oid] */
+ if (newtup->t_data->t_hoff - SizeofHeapTupleHeader > 0)
+ {
+ XLogRegisterBufData(0,
+ ((char *) newtup->t_data) + SizeofHeapTupleHeader,
+ newtup->t_data->t_hoff - SizeofHeapTupleHeader);
+ }
- /* data after common prefix */
- XLogRegisterBufData(0,
+ /* data after common prefix */
+ XLogRegisterBufData(0,
((char *) newtup->t_data) + newtup->t_data->t_hoff + prefixlen,
newtup->t_len - newtup->t_data->t_hoff - prefixlen - suffixlen);
+ }
}
+ /*
+ * If the old and new tuple are on different pages, also register the old
+ * page, so that a full-page image is created for it if necessary. We
+ * don't need any extra information to replay changes to it.
+ */
+ if (oldbuf != newbuf && HeapNeedsWAL(reln, oldbuf))
+ XLogRegisterBuffer(1, oldbuf, REGBUF_STANDARD);
+
/* We need to log a tuple identity */
if (need_tuple_data && old_key_tuple)
{
@@ -8343,8 +8371,13 @@ heap_xlog_update(XLogReaderState *record, bool hot_update)
*/
/* Deal with old tuple version */
- oldaction = XLogReadBufferForRedo(record, (oldblk == newblk) ? 0 : 1,
- &obuffer);
+ if (oldblk == newblk)
+ oldaction = XLogReadBufferForRedo(record, 0, &obuffer);
+ else if (XLogRecHasBlockRef(record, 1))
+ oldaction = XLogReadBufferForRedo(record, 1, &obuffer);
+ else
+ oldaction = BLK_DONE;
+
if (oldaction == BLK_NEEDS_REDO)
{
page = BufferGetPage(obuffer);
@@ -8398,6 +8431,8 @@ heap_xlog_update(XLogReaderState *record, bool hot_update)
PageInit(page, BufferGetPageSize(nbuffer), 0);
newaction = BLK_NEEDS_REDO;
}
+ else if (!XLogRecHasBlockRef(record, 0))
+ newaction = BLK_DONE;
else
newaction = XLogReadBufferForRedo(record, 0, &nbuffer);
@@ -8788,9 +8823,16 @@ heap2_redo(XLogReaderState *record)
* heap_sync - sync a heap, for use when no WAL has been written
*
* This forces the heap contents (including TOAST heap if any) down to disk.
- * If we skipped using WAL, and WAL is otherwise needed, we must force the
- * relation down to disk before it's safe to commit the transaction. This
- * requires writing out any dirty buffers and then doing a forced fsync.
+ * If we did any changes to the heap bypassing the buffer manager, we must
+ * force the relation down to disk before it's safe to commit the
+ * transaction, because the direct modifications will not be flushed by
+ * the next checkpoint.
+ *
+ * We used to also use this after batch operations like COPY and CLUSTER,
+ * if we skipped using WAL and WAL is otherwise needed, but there were
+ * corner-cases involving other WAL-logged operations to the same
+ * relation, where that was not enough. heap_register_sync() should be
+ * used for that purpose instead.
*
* Indexes are not touched. (Currently, index operations associated with
* the commands that use this are WAL-logged and so do not need fsync.
@@ -8823,3 +8865,75 @@ heap_sync(Relation rel)
heap_close(toastrel, AccessShareLock);
}
}
+
+/*
+ * heap_register_sync - register a heap to be synced to disk at commit
+ *
+ * This can be used to skip WAL-logging changes on a relation file that has
+ * been created in the same transaction. This makes note of the current size of
+ * the relation, and ensures that when the relation is extended, any changes
+ * to the new blocks in the heap, in the same transaction, will not be
+ * WAL-logged. Instead, the heap contents are flushed to disk at commit,
+ * like heap_sync() does.
+ *
+ * This does the same for the TOAST heap, if any. Indexes are not affected.
+ */
+void
+heap_register_sync(Relation rel)
+{
+ /* non-WAL-logged tables never need fsync */
+ if (!RelationNeedsWAL(rel))
+ return;
+
+ smgrRegisterPendingSync(rel->rd_node, RelationGetNumberOfBlocks(rel));
+ if (OidIsValid(rel->rd_rel->reltoastrelid))
+ {
+ Relation toastrel;
+
+ toastrel = heap_open(rel->rd_rel->reltoastrelid, AccessShareLock);
+ smgrRegisterPendingSync(toastrel->rd_node,
+ RelationGetNumberOfBlocks(toastrel));
+ heap_close(toastrel, AccessShareLock);
+ }
+}
+
+/*
+ * Do changes to given heap page need to be WAL-logged?
+ *
+ * This takes into account any previous heap_register_sync() requests.
+ *
+ * Note that it is required to check this before creating any WAL records
+ * for heap pages - it is not merely an optimization! WAL-logging a record,
+ * when we have already skipped a previous WAL record for the same page
+ * could lead lead to failure at WAL replay, as the "before" state expected
+ * by the record might not match what's on disk. Also, if the heap was
+ * truncated earlier, we must WAL-log any changes to the once-truncated
+ * blocks, because replaying the truncation record will destroy them.
+ * (smgrIsSyncPending() figures out all that.)
+ */
+bool
+HeapNeedsWAL(Relation rel, Buffer buf)
+{
+ /* Temporary relations never need WAL */
+ if (!RelationNeedsWAL(rel))
+ return false;
+
+ /*
+ * If we are going to fsync() the relation at COMMIT, and we have not
+ * truncated the block away previously, and we have not emitted any WAL
+ * records for this block yet, we can skip WAL-logging it.
+ */
+ if (smgrIsSyncPending(rel->rd_node, BufferGetBlockNumber(buf)))
+ {
+ /*
+ * If a pending fsync() will handle this page, its LSN should be
+ * invalid. If it's not, we've already emitted a WAL record for this
+ * block, and all subsequent changes to the block must be WAL-logged
+ * too.
+ */
+ Assert(PageGetLSN(BufferGetPage(buf)) == InvalidXLogRecPtr);
+ return false;
+ }
+
+ return true;
+}
diff --git a/src/backend/access/heap/pruneheap.c b/src/backend/access/heap/pruneheap.c
index 59beadd..476e308 100644
--- a/src/backend/access/heap/pruneheap.c
+++ b/src/backend/access/heap/pruneheap.c
@@ -251,7 +251,7 @@ heap_page_prune(Relation relation, Buffer buffer, TransactionId OldestXmin,
/*
* Emit a WAL HEAP_CLEAN record showing what we did
*/
- if (RelationNeedsWAL(relation))
+ if (HeapNeedsWAL(relation, buffer))
{
XLogRecPtr recptr;
diff --git a/src/backend/access/heap/rewriteheap.c b/src/backend/access/heap/rewriteheap.c
index f9ce986..36ba62a 100644
--- a/src/backend/access/heap/rewriteheap.c
+++ b/src/backend/access/heap/rewriteheap.c
@@ -649,9 +649,7 @@ raw_heap_insert(RewriteState state, HeapTuple tup)
}
else if (HeapTupleHasExternal(tup) || tup->t_len > TOAST_TUPLE_THRESHOLD)
heaptup = toast_insert_or_update(state->rs_new_rel, tup, NULL,
- HEAP_INSERT_SKIP_FSM |
- (state->rs_use_wal ?
- 0 : HEAP_INSERT_SKIP_WAL));
+ HEAP_INSERT_SKIP_FSM);
else
heaptup = tup;
diff --git a/src/backend/access/heap/visibilitymap.c b/src/backend/access/heap/visibilitymap.c
index fc28f3f..7663485 100644
--- a/src/backend/access/heap/visibilitymap.c
+++ b/src/backend/access/heap/visibilitymap.c
@@ -279,7 +279,7 @@ visibilitymap_set(Relation rel, BlockNumber heapBlk, Buffer heapBuf,
map[mapByte] |= (1 << mapBit);
MarkBufferDirty(vmBuf);
- if (RelationNeedsWAL(rel))
+ if (HeapNeedsWAL(rel, heapBuf))
{
if (XLogRecPtrIsInvalid(recptr))
{
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index b0d5440..5013145 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1989,6 +1989,9 @@ CommitTransaction(void)
/* close large objects before lower-level cleanup */
AtEOXact_LargeObject(true);
+ /* Flush updates to relations that we didn't WAL-logged */
+ smgrDoPendingSyncs(true);
+
/*
* Mark serializable transaction as complete for predicate locking
* purposes. This should be done as late as we can put it and still allow
@@ -2219,6 +2222,9 @@ PrepareTransaction(void)
/* close large objects before lower-level cleanup */
AtEOXact_LargeObject(true);
+ /* Flush updates to relations that we didn't WAL-logged */
+ smgrDoPendingSyncs(true);
+
/*
* Mark serializable transaction as complete for predicate locking
* purposes. This should be done as late as we can put it and still allow
@@ -2519,6 +2525,7 @@ AbortTransaction(void)
AtAbort_Notify();
AtEOXact_RelationMap(false);
AtAbort_Twophase();
+ smgrDoPendingSyncs(false);
/*
* Advertise the fact that we aborted in pg_clog (assuming that we got as
diff --git a/src/backend/catalog/storage.c b/src/backend/catalog/storage.c
index fe68c99..3097d84 100644
--- a/src/backend/catalog/storage.c
+++ b/src/backend/catalog/storage.c
@@ -19,6 +19,7 @@
#include "postgres.h"
+#include "access/transam.h"
#include "access/visibilitymap.h"
#include "access/xact.h"
#include "access/xlog.h"
@@ -29,6 +30,7 @@
#include "catalog/storage_xlog.h"
#include "storage/freespace.h"
#include "storage/smgr.h"
+#include "utils/hsearch.h"
#include "utils/memutils.h"
#include "utils/rel.h"
@@ -64,6 +66,49 @@ typedef struct PendingRelDelete
static PendingRelDelete *pendingDeletes = NULL; /* head of linked list */
/*
+ * We also track relation files (RelFileNode values) that have been created
+ * in the same transaction, and that have been modified without WAL-logging
+ * the action (an optimization possible with wal_level=minimal). When we are
+ * about to skip WAL-logging, a PendingRelSync entry is created, and
+ * 'sync_above' is set to the current size of the relation. Any operations
+ * on blocks < sync_above need to be WAL-logged as usual, but for operations
+ * on higher blocks, WAL-logging is skipped.
+ *
+ * NB: after WAL-logging has been skipped for a block, we must not WAL-log
+ * any subsequent actions on the same block either. Replaying the WAL record
+ * of the subsequent action might fail otherwise, as the "before" state of
+ * the block might not match, as the earlier actions were not WAL-logged.
+ * Likewise, after we have WAL-logged an operation for a block, we must
+ * WAL-log any subsequent operations on the same page as well. Replaying
+ * a possible full-page-image from the earlier WAL record would otherwise
+ * revert the page to the old state, even if we sync the relation at end
+ * of transaction.
+ *
+ * If a relation is truncated (without creating a new relfilenode), and we
+ * emit a WAL record of the truncation, we can't skip WAL-logging for any
+ * of the truncated blocks anymore, as replaying the truncation record will
+ * destroy all the data inserted after that. But if we have already decided
+ * to skip WAL-logging changes to a relation, and the relation is truncated,
+ * we don't need to WAL-log the truncation either.
+ *
+ * This mechanism is currently only used by heaps. Indexes are always
+ * WAL-logged. Also, this only applies for wal_level=minimal; with higher
+ * WAL levels we need the WAL for PITR/replication anyway.
+ */
+typedef struct PendingRelSync
+{
+ RelFileNode relnode; /* relation created in same xact */
+ BlockNumber sync_above; /* WAL-logging skipped for blocks >=
+ * sync_above */
+ BlockNumber truncated_to; /* truncation WAL record was written */
+} PendingRelSync;
+
+/* Relations that need to be fsync'd at commit */
+static HTAB *pendingSyncs = NULL;
+
+static void createPendingSyncsHash(void);
+
+/*
* RelationCreateStorage
* Create physical storage for a relation.
*
@@ -226,6 +271,8 @@ RelationPreserveStorage(RelFileNode rnode, bool atCommit)
void
RelationTruncate(Relation rel, BlockNumber nblocks)
{
+ PendingRelSync *pending = NULL;
+ bool found;
bool fsm;
bool vm;
@@ -260,30 +307,51 @@ RelationTruncate(Relation rel, BlockNumber nblocks)
*/
if (RelationNeedsWAL(rel))
{
- /*
- * Make an XLOG entry reporting the file truncation.
- */
- XLogRecPtr lsn;
- xl_smgr_truncate xlrec;
-
- xlrec.blkno = nblocks;
- xlrec.rnode = rel->rd_node;
-
- XLogBeginInsert();
- XLogRegisterData((char *) &xlrec, sizeof(xlrec));
-
- lsn = XLogInsert(RM_SMGR_ID,
- XLOG_SMGR_TRUNCATE | XLR_SPECIAL_REL_UPDATE);
+ if (!pendingSyncs)
+ createPendingSyncsHash();
+ pending = (PendingRelSync *) hash_search(pendingSyncs,
+ (void *) &rel->rd_node,
+ HASH_ENTER, &found);
+ if (!found)
+ {
+ pending->sync_above = InvalidBlockNumber;
+ pending->truncated_to = InvalidBlockNumber;
+ }
- /*
- * Flush, because otherwise the truncation of the main relation might
- * hit the disk before the WAL record, and the truncation of the FSM
- * or visibility map. If we crashed during that window, we'd be left
- * with a truncated heap, but the FSM or visibility map would still
- * contain entries for the non-existent heap pages.
- */
- if (fsm || vm)
- XLogFlush(lsn);
+ if (pending->sync_above == InvalidBlockNumber || pending->sync_above < nblocks)
+ {
+ /*
+ * Make an XLOG entry reporting the file truncation.
+ */
+ XLogRecPtr lsn;
+ xl_smgr_truncate xlrec;
+
+ xlrec.blkno = nblocks;
+ xlrec.rnode = rel->rd_node;
+
+ XLogBeginInsert();
+ XLogRegisterData((char *) &xlrec, sizeof(xlrec));
+
+ lsn = XLogInsert(RM_SMGR_ID,
+ XLOG_SMGR_TRUNCATE | XLR_SPECIAL_REL_UPDATE);
+
+ elog(DEBUG2, "WAL-logged truncation of rel %u/%u/%u to %u blocks",
+ rel->rd_node.spcNode, rel->rd_node.dbNode, rel->rd_node.relNode,
+ nblocks);
+
+ /*
+ * Flush, because otherwise the truncation of the main relation
+ * might hit the disk before the WAL record, and the truncation of
+ * the FSM or visibility map. If we crashed during that window,
+ * we'd be left with a truncated heap, but the FSM or visibility
+ * map would still contain entries for the non-existent heap
+ * pages.
+ */
+ if (fsm || vm)
+ XLogFlush(lsn);
+
+ pending->truncated_to = nblocks;
+ }
}
/* Do the real work */
@@ -361,7 +429,9 @@ smgrDoPendingDeletes(bool isCommit)
smgrdounlinkall(srels, nrels, false);
for (i = 0; i < nrels; i++)
+ {
smgrclose(srels[i]);
+ }
pfree(srels);
}
@@ -418,6 +488,140 @@ smgrGetPendingDeletes(bool forCommit, RelFileNode **ptr)
return nrels;
}
+/* create the hash table to track pending at-commit fsyncs */
+static void
+createPendingSyncsHash(void)
+{
+ /* First time through: initialize the hash table */
+ HASHCTL ctl;
+
+ MemSet(&ctl, 0, sizeof(ctl));
+ ctl.keysize = sizeof(RelFileNode);
+ ctl.entrysize = sizeof(PendingRelSync);
+ ctl.hash = tag_hash;
+ pendingSyncs = hash_create("pending relation sync table", 5,
+ &ctl, HASH_ELEM | HASH_FUNCTION);
+}
+
+/*
+ * Remember that the given relation needs to be sync'd at commit, because
+ * we are going to skip WAL-logging subsequent actions to it.
+ */
+void
+smgrRegisterPendingSync(RelFileNode rnode, BlockNumber nblocks)
+{
+ PendingRelSync *pending;
+ bool found;
+
+ if (!pendingSyncs)
+ createPendingSyncsHash();
+
+ /* Look up or create an entry */
+ pending = (PendingRelSync *) hash_search(pendingSyncs,
+ (void *) &rnode,
+ HASH_ENTER, &found);
+ if (!found)
+ {
+ pending->truncated_to = InvalidBlockNumber;
+ pending->sync_above = nblocks;
+
+ elog(DEBUG2, "registering new pending sync for rel %u/%u/%u at block %u",
+ rnode.spcNode, rnode.dbNode, rnode.relNode, nblocks);
+
+ }
+ else if (pending->sync_above == InvalidBlockNumber)
+ {
+ elog(DEBUG2, "registering pending sync for rel %u/%u/%u at block %u",
+ rnode.spcNode, rnode.dbNode, rnode.relNode, nblocks);
+ pending->sync_above = nblocks;
+ }
+ else
+ elog(DEBUG2, "pending sync for rel %u/%u/%u was already registered at block %u (new %u)",
+ rnode.spcNode, rnode.dbNode, rnode.relNode, pending->sync_above,
+ nblocks);
+}
+
+/*
+ * Are we going to fsync() this relation at COMMIT, and hence don't need to
+ * WAL-log changes to the given block?
+ */
+bool
+smgrIsSyncPending(RelFileNode rnode, BlockNumber blkno)
+{
+ PendingRelSync *pending;
+ bool found;
+
+ if (!pendingSyncs)
+ return false;
+
+ pending = (PendingRelSync *) hash_search(pendingSyncs,
+ (void *) &rnode,
+ HASH_FIND, &found);
+ if (!found)
+ return false;
+
+ /*
+ * We have no fsync() pending for this relation, or we have (possibly)
+ * already emitted WAL records for this block.
+ */
+ if (pending->sync_above == InvalidBlockNumber ||
+ pending->sync_above > blkno)
+ {
+ elog(DEBUG2, "not skipping WAL-logging for rel %u/%u/%u block %u, because sync_above is %u",
+ rnode.spcNode, rnode.dbNode, rnode.relNode, blkno, pending->sync_above);
+ return false;
+ }
+
+ /*
+ * We have emitted a truncation record for this block.
+ */
+ if (pending->truncated_to != InvalidBlockNumber &&
+ pending->truncated_to <= blkno)
+ {
+ elog(DEBUG2, "not skipping WAL-logging for rel %u/%u/%u block %u, because it was truncated earlier in the same xact",
+ rnode.spcNode, rnode.dbNode, rnode.relNode, blkno);
+ return false;
+ }
+
+ elog(DEBUG2, "skipping WAL-logging for rel %u/%u/%u block %u",
+ rnode.spcNode, rnode.dbNode, rnode.relNode, blkno);
+
+ return true;
+}
+
+/*
+ * Sync to disk any relations that we skipped WAL-logging for earlier.
+ */
+void
+smgrDoPendingSyncs(bool isCommit)
+{
+ if (!pendingSyncs)
+ return;
+
+ if (isCommit)
+ {
+ HASH_SEQ_STATUS status;
+ PendingRelSync *pending;
+
+ hash_seq_init(&status, pendingSyncs);
+
+ while ((pending = hash_seq_search(&status)) != NULL)
+ {
+ if (pending->sync_above != InvalidBlockNumber)
+ {
+ FlushRelationBuffersWithoutRelCache(pending->relnode, false);
+ smgrimmedsync(smgropen(pending->relnode, InvalidBackendId), MAIN_FORKNUM);
+
+ elog(DEBUG2, "syncing rel %u/%u/%u", pending->relnode.spcNode,
+ pending->relnode.dbNode, pending->relnode.relNode);
+ }
+ }
+ }
+
+ hash_destroy(pendingSyncs);
+ pendingSyncs = NULL;
+}
+
/*
* PostPrepare_smgr -- Clean up after a successful PREPARE
*
diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index 3201476..cc8cebd 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -26,6 +26,7 @@
#include "access/xact.h"
#include "access/xlog.h"
#include "catalog/pg_type.h"
+#include "catalog/storage.h"
#include "commands/copy.h"
#include "commands/defrem.h"
#include "commands/trigger.h"
@@ -2269,8 +2270,7 @@ CopyFrom(CopyState cstate)
* - data is being written to relfilenode created in this transaction
* then we can skip writing WAL. It's safe because if the transaction
* doesn't commit, we'll discard the table (or the new relfilenode file).
- * If it does commit, we'll have done the heap_sync at the bottom of this
- * routine first.
+ * If it does commit, commit will do heap_sync().
*
* As mentioned in comments in utils/rel.h, the in-same-transaction test
* is not always set correctly, since in rare cases rd_newRelfilenodeSubid
@@ -2302,7 +2302,7 @@ CopyFrom(CopyState cstate)
{
hi_options |= HEAP_INSERT_SKIP_FSM;
if (!XLogIsNeeded())
- hi_options |= HEAP_INSERT_SKIP_WAL;
+ heap_register_sync(cstate->rel);
}
/*
@@ -2551,11 +2551,11 @@ CopyFrom(CopyState cstate)
FreeExecutorState(estate);
/*
- * If we skipped writing WAL, then we need to sync the heap (but not
- * indexes since those use WAL anyway)
+ * If we skipped writing WAL, then we will sync the heap at the end of
+ * the transaction. (We used to do it here, but it was later found out
+ * that to be safe, we must also avoid WAL-logging any subsequent
+ * actions on the pages we skipped WAL for). Indexes always use WAL.
*/
- if (hi_options & HEAP_INSERT_SKIP_WAL)
- heap_sync(cstate->rel);
return processed;
}
diff --git a/src/backend/commands/createas.c b/src/backend/commands/createas.c
index fcb0331..80713af 100644
--- a/src/backend/commands/createas.c
+++ b/src/backend/commands/createas.c
@@ -471,8 +471,9 @@ intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
* We can skip WAL-logging the insertions, unless PITR or streaming
* replication is in use. We can skip the FSM in any case.
*/
- myState->hi_options = HEAP_INSERT_SKIP_FSM |
- (XLogIsNeeded() ? 0 : HEAP_INSERT_SKIP_WAL);
+ if (!XLogIsNeeded())
+ heap_register_sync(intoRelationDesc);
+ myState->hi_options = HEAP_INSERT_SKIP_FSM;
myState->bistate = GetBulkInsertState();
/* Not using WAL requires smgr_targblock be initially invalid */
@@ -519,9 +520,7 @@ intorel_shutdown(DestReceiver *self)
FreeBulkInsertState(myState->bistate);
- /* If we skipped using WAL, must heap_sync before commit */
- if (myState->hi_options & HEAP_INSERT_SKIP_WAL)
- heap_sync(myState->rel);
+ /* If we skipped using WAL, we will sync the relation at commit */
/* close rel, but keep lock until commit */
heap_close(myState->rel, NoLock);
diff --git a/src/backend/commands/matview.c b/src/backend/commands/matview.c
index 869c586..7be9f1f 100644
--- a/src/backend/commands/matview.c
+++ b/src/backend/commands/matview.c
@@ -412,7 +412,7 @@ transientrel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
*/
myState->hi_options = HEAP_INSERT_SKIP_FSM | HEAP_INSERT_FROZEN;
if (!XLogIsNeeded())
- myState->hi_options |= HEAP_INSERT_SKIP_WAL;
+ heap_register_sync(transientrel);
myState->bistate = GetBulkInsertState();
/* Not using WAL requires smgr_targblock be initially invalid */
@@ -453,9 +453,7 @@ transientrel_shutdown(DestReceiver *self)
FreeBulkInsertState(myState->bistate);
- /* If we skipped using WAL, must heap_sync before commit */
- if (myState->hi_options & HEAP_INSERT_SKIP_WAL)
- heap_sync(myState->transientrel);
+ /* If we skipped using WAL, we will sync the relation at commit */
/* close transientrel, but keep lock until commit */
heap_close(myState->transientrel, NoLock);
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index eeda3b4..adff984 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -3983,8 +3983,9 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
bistate = GetBulkInsertState();
hi_options = HEAP_INSERT_SKIP_FSM;
+
if (!XLogIsNeeded())
- hi_options |= HEAP_INSERT_SKIP_WAL;
+ heap_register_sync(newrel);
}
else
{
@@ -4235,8 +4236,6 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
FreeBulkInsertState(bistate);
/* If we skipped writing WAL, then we need to sync the heap. */
- if (hi_options & HEAP_INSERT_SKIP_WAL)
- heap_sync(newrel);
heap_close(newrel, NoLock);
}
diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 4f6f6e7..8410812 100644
--- a/src/backend/commands/vacuumlazy.c
+++ b/src/backend/commands/vacuumlazy.c
@@ -761,7 +761,7 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
* page has been previously WAL-logged, and if not, do that
* now.
*/
- if (RelationNeedsWAL(onerel) &&
+ if (HeapNeedsWAL(onerel, buf) &&
PageGetLSN(page) == InvalidXLogRecPtr)
log_newpage_buffer(buf, true);
@@ -981,7 +981,7 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
}
/* Now WAL-log freezing if necessary */
- if (RelationNeedsWAL(onerel))
+ if (HeapNeedsWAL(onerel, buf))
{
XLogRecPtr recptr;
@@ -1283,7 +1283,7 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
MarkBufferDirty(buffer);
/* XLOG stuff */
- if (RelationNeedsWAL(onerel))
+ if (HeapNeedsWAL(onerel, buffer))
{
XLogRecPtr recptr;
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 7141eb8..e1061d7 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -413,6 +413,7 @@ static BufferDesc *BufferAlloc(SMgrRelation smgr,
BufferAccessStrategy strategy,
bool *foundPtr);
static void FlushBuffer(BufferDesc *buf, SMgrRelation reln);
+static void FlushRelationBuffers_common(SMgrRelation smgr, bool islocal);
static void AtProcExit_Buffers(int code, Datum arg);
static void CheckForBufferLeaks(void);
static int rnode_comparator(const void *p1, const void *p2);
@@ -2864,18 +2865,39 @@ PrintPinnedBufs(void)
void
FlushRelationBuffers(Relation rel)
{
- int i;
- BufferDesc *bufHdr;
-
/* Open rel at the smgr level if not already done */
RelationOpenSmgr(rel);
- if (RelationUsesLocalBuffers(rel))
+ FlushRelationBuffers_common(rel->rd_smgr, RelationUsesLocalBuffers(rel));
+}
+
+/*
+ * Like FlushRelationBuffers(), but the relation is specified by a
+ * RelFileNode
+ */
+void
+FlushRelationBuffersWithoutRelCache(RelFileNode rnode, bool islocal)
+{
+ FlushRelationBuffers_common(smgropen(rnode, InvalidBackendId), islocal);
+}
+
+/*
+ * Code shared between the FlushRelationBuffers() and
+ * FlushRelationBuffersWithoutRelCache() functions.
+ */
+static void
+FlushRelationBuffers_common(SMgrRelation smgr, bool islocal)
+{
+ RelFileNode rnode = smgr->smgr_rnode.node;
+ int i;
+ BufferDesc *bufHdr;
+
+ if (islocal)
{
for (i = 0; i < NLocBuffer; i++)
{
bufHdr = GetLocalBufferDescriptor(i);
- if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) &&
+ if (RelFileNodeEquals(bufHdr->tag.rnode, rnode) &&
(bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_DIRTY))
{
ErrorContextCallback errcallback;
@@ -2891,7 +2913,7 @@ FlushRelationBuffers(Relation rel)
PageSetChecksumInplace(localpage, bufHdr->tag.blockNum);
- smgrwrite(rel->rd_smgr,
+ smgrwrite(smgr,
bufHdr->tag.forkNum,
bufHdr->tag.blockNum,
localpage,
@@ -2918,18 +2940,18 @@ FlushRelationBuffers(Relation rel)
* As in DropRelFileNodeBuffers, an unlocked precheck should be safe
* and saves some cycles.
*/
- if (!RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node))
+ if (!RelFileNodeEquals(bufHdr->tag.rnode, rnode))
continue;
ReservePrivateRefCountEntry();
LockBufHdr(bufHdr);
- if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node) &&
+ if (RelFileNodeEquals(bufHdr->tag.rnode, rnode) &&
(bufHdr->flags & BM_VALID) && (bufHdr->flags & BM_DIRTY))
{
PinBuffer_Locked(bufHdr);
LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
- FlushBuffer(bufHdr, rel->rd_smgr);
+ FlushBuffer(bufHdr, smgr);
LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
UnpinBuffer(bufHdr, true);
}
@@ -3122,6 +3144,9 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
XLogRecPtr lsn = InvalidXLogRecPtr;
bool dirtied = false;
bool delayChkpt = false;
+ RelFileNode rnode;
+ ForkNumber forknum;
+ BlockNumber blknum;
/*
* If we need to protect hint bit updates from torn writes, WAL-log a
@@ -3132,7 +3157,9 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
* We don't check full_page_writes here because that logic is included
* when we call XLogInsert() since the value changes dynamically.
*/
- if (XLogHintBitIsNeeded() && (bufHdr->flags & BM_PERMANENT))
+ BufferGetTag(buffer, &rnode, &forknum, &blknum);
+ if (XLogHintBitIsNeeded() && (bufHdr->flags & BM_PERMANENT) &&
+ !smgrIsSyncPending(rnode, blknum))
{
/*
* If we're in recovery we cannot dirty a page because of a hint.
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index a427df5..b671210 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -25,10 +25,9 @@
/* "options" flag bits for heap_insert */
-#define HEAP_INSERT_SKIP_WAL 0x0001
-#define HEAP_INSERT_SKIP_FSM 0x0002
-#define HEAP_INSERT_FROZEN 0x0004
-#define HEAP_INSERT_SPECULATIVE 0x0008
+#define HEAP_INSERT_SKIP_FSM 0x0001
+#define HEAP_INSERT_FROZEN 0x0002
+#define HEAP_INSERT_SPECULATIVE 0x0004
typedef struct BulkInsertStateData *BulkInsertState;
@@ -176,6 +175,7 @@ extern void simple_heap_delete(Relation relation, ItemPointer tid);
extern void simple_heap_update(Relation relation, ItemPointer otid,
HeapTuple tup);
+extern void heap_register_sync(Relation relation);
extern void heap_sync(Relation relation);
/* in heap/pruneheap.c */
diff --git a/src/include/access/heapam_xlog.h b/src/include/access/heapam_xlog.h
index f77489b..81b7c81 100644
--- a/src/include/access/heapam_xlog.h
+++ b/src/include/access/heapam_xlog.h
@@ -372,6 +372,8 @@ extern void heap2_desc(StringInfo buf, XLogReaderState *record);
extern const char *heap2_identify(uint8 info);
extern void heap_xlog_logical_rewrite(XLogReaderState *r);
+extern bool HeapNeedsWAL(Relation rel, Buffer buf);
+
extern XLogRecPtr log_heap_cleanup_info(RelFileNode rnode,
TransactionId latestRemovedXid);
extern XLogRecPtr log_heap_clean(Relation reln, Buffer buffer,
diff --git a/src/include/catalog/storage.h b/src/include/catalog/storage.h
index ef960da..e84dee2 100644
--- a/src/include/catalog/storage.h
+++ b/src/include/catalog/storage.h
@@ -29,6 +29,9 @@ extern void RelationTruncate(Relation rel, BlockNumber nblocks);
*/
extern void smgrDoPendingDeletes(bool isCommit);
extern int smgrGetPendingDeletes(bool forCommit, RelFileNode **ptr);
+extern void smgrRegisterPendingSync(RelFileNode rnode, BlockNumber nblocks);
+extern bool smgrIsSyncPending(RelFileNode rnode, BlockNumber blkno);
+extern void smgrDoPendingSyncs(bool isCommit);
extern void AtSubCommit_smgr(void);
extern void AtSubAbort_smgr(void);
extern void PostPrepare_smgr(void);
diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h
index 92c4bc5..7a3daaa 100644
--- a/src/include/storage/bufmgr.h
+++ b/src/include/storage/bufmgr.h
@@ -178,6 +178,8 @@ extern BlockNumber RelationGetNumberOfBlocksInFork(Relation relation,
ForkNumber forkNum);
extern void FlushOneBuffer(Buffer buffer);
extern void FlushRelationBuffers(Relation rel);
+extern void FlushRelationBuffersWithoutRelCache(RelFileNode rnode,
+ bool islocal);
extern void FlushDatabaseBuffers(Oid dbid);
extern void DropRelFileNodeBuffers(RelFileNodeBackend rnode,
ForkNumber forkNum, BlockNumber firstDelBlock);
--
2.1.4
--
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