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Revert "Skip WAL for new relfilenodes, under wal_level=minimal."

Browse Source 
This reverts commit cb2fd7eac2.  Per
numerous buildfarm members, it was incompatible with parallel query, and
a test case assumed LP64.  Back-patch to 9.5 (all supported versions).

Discussion: https://postgr.es/m/20200321224920.GB1763544@rfd.leadboat.com
This commit is contained in:
Noah Misch
2020-03-22 09:24:09 -07:00
parent 03b89f1949
commit 2fbdebc248
48 changed files with 334 additions and 1401 deletions
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2
src/backend/access/gist/gistbuild.c
View File

@@ -191,7 +191,7 @@ gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
PageSetLSN(page, recptr);
}
else
PageSetLSN(page, gistGetFakeLSN(index));
PageSetLSN(page, gistGetFakeLSN(heap));
UnlockReleaseBuffer(buffer);

31
src/backend/access/gist/gistutil.c
View File

@@ -972,44 +972,23 @@ gistproperty(Oid index_oid, int attno,
}
/*
* Some indexes are not WAL-logged, but we need LSNs to detect concurrent page
* splits anyway. This function provides a fake sequence of LSNs for that
* purpose.
* Temporary and unlogged GiST indexes are not WAL-logged, but we need LSNs
* to detect concurrent page splits anyway. This function provides a fake
* sequence of LSNs for that purpose.
*/
XLogRecPtr
gistGetFakeLSN(Relation rel)
{
static XLogRecPtr counter = 1;
if (rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP)
{
/*
* Temporary relations are only accessible in our session, so a simple
* backend-local counter will do.
*/
static XLogRecPtr counter = 1;
return counter++;
}
else if (rel->rd_rel->relpersistence == RELPERSISTENCE_PERMANENT)
{
/*
* WAL-logging on this relation will start after commit, so its LSNs
* must be distinct numbers smaller than the LSN at the next commit.
* Emit a dummy WAL record if insert-LSN hasn't advanced after the
* last call.
*/
static XLogRecPtr lastlsn = InvalidXLogRecPtr;
XLogRecPtr currlsn = GetXLogInsertRecPtr();
/* Shouldn't be called for WAL-logging relations */
Assert(!RelationNeedsWAL(rel));
/* No need for an actual record if we already have a distinct LSN */
if (!XLogRecPtrIsInvalid(lastlsn) && lastlsn == currlsn)
currlsn = gistXLogAssignLSN();
lastlsn = currlsn;
return currlsn;
}
else
{
/*

21
src/backend/access/gist/gistxlog.c
View File

@@ -505,9 +505,6 @@ gist_redo(XLogReaderState *record)
case XLOG_GIST_CREATE_INDEX:
gistRedoCreateIndex(record);
break;
case XLOG_GIST_ASSIGN_LSN:
/* nop. See gistGetFakeLSN(). */
break;
default:
elog(PANIC, "gist_redo: unknown op code %u", info);
}
@@ -626,24 +623,6 @@ gistXLogSplit(bool page_is_leaf,
return recptr;
}
/*
* Write an empty XLOG record to assign a distinct LSN.
*/
XLogRecPtr
gistXLogAssignLSN(void)
{
int dummy = 0;
/*
* Records other than SWITCH_WAL must have content. We use an integer 0 to
* follow the restriction.
*/
XLogBeginInsert();
XLogSetRecordFlags(XLOG_MARK_UNIMPORTANT);
XLogRegisterData((char *) &dummy, sizeof(dummy));
return XLogInsert(RM_GIST_ID, XLOG_GIST_ASSIGN_LSN);
}
/*
* Write XLOG record describing a page update. The update can include any
* number of deletions and/or insertions of tuples on a single index page.

28
src/backend/access/heap/heapam.c
View File

@@ -27,6 +27,7 @@
* heap_multi_insert - insert multiple tuples into a relation
* heap_delete - delete a tuple from a relation
* heap_update - replace a tuple in a relation with another tuple
* heap_sync - sync heap, for when no WAL has been written
*
* NOTES
* This file contains the heap_ routines which implement
@@ -2395,6 +2396,12 @@ ReleaseBulkInsertStatePin(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.
*
@@ -2503,7 +2510,7 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
MarkBufferDirty(buffer);
/* XLOG stuff */
if (RelationNeedsWAL(relation))
if (!(options & HEAP_INSERT_SKIP_WAL) && RelationNeedsWAL(relation))
{
xl_heap_insert xlrec;
xl_heap_header xlhdr;
@@ -2713,7 +2720,7 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
/* currently not needed (thus unsupported) for heap_multi_insert() */
AssertArg(!(options & HEAP_INSERT_NO_LOGICAL));
needwal = RelationNeedsWAL(relation);
needwal = !(options & HEAP_INSERT_SKIP_WAL) && RelationNeedsWAL(relation);
saveFreeSpace = RelationGetTargetPageFreeSpace(relation,
HEAP_DEFAULT_FILLFACTOR);
@@ -9413,13 +9420,18 @@ heap2_redo(XLogReaderState *record)
}
/*
* heap_sync - for binary compatibility
* heap_sync - sync a heap, for use when no WAL has been written
*
* A newer PostgreSQL version removes this function. It exists here just in
* case an extension calls it. See "Skipping WAL for New RelFileNode" in
* src/backend/access/transam/README for the system that superseded it,
* allowing removal of most calls. Cases like copy_relation_data() should
* call smgrimmedsync() directly.
* 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.
*
* Indexes are not touched. (Currently, index operations associated with
* the commands that use this are WAL-logged and so do not need fsync.
* That behavior might change someday, but in any case it's likely that
* any fsync decisions required would be per-index and hence not appropriate
* to be done here.)
*/
void
heap_sync(Relation rel)

21
src/backend/access/heap/rewriteheap.c
View File

@@ -145,6 +145,7 @@ typedef struct RewriteStateData
Page rs_buffer; /* page currently being built */
BlockNumber rs_blockno; /* block where page will go */
bool rs_buffer_valid; /* T if any tuples in buffer */
bool rs_use_wal; /* must we WAL-log inserts? */
bool rs_logical_rewrite; /* do we need to do logical rewriting */
TransactionId rs_oldest_xmin; /* oldest xmin used by caller to determine
* tuple visibility */
@@ -238,13 +239,15 @@ static void logical_end_heap_rewrite(RewriteState state);
* oldest_xmin xid used by the caller to determine which tuples are dead
* freeze_xid xid before which tuples will be frozen
* min_multi multixact before which multis will be removed
* use_wal should the inserts to the new heap be WAL-logged?
*
* Returns an opaque RewriteState, allocated in current memory context,
* to be used in subsequent calls to the other functions.
*/
RewriteState
begin_heap_rewrite(Relation old_heap, Relation new_heap, TransactionId oldest_xmin,
TransactionId freeze_xid, MultiXactId cutoff_multi)
TransactionId freeze_xid, MultiXactId cutoff_multi,
bool use_wal)
{
RewriteState state;
MemoryContext rw_cxt;
@@ -269,6 +272,7 @@ begin_heap_rewrite(Relation old_heap, Relation new_heap, TransactionId oldest_xm
/* new_heap needn't be empty, just locked */
state->rs_blockno = RelationGetNumberOfBlocks(new_heap);
state->rs_buffer_valid = false;
state->rs_use_wal = use_wal;
state->rs_oldest_xmin = oldest_xmin;
state->rs_freeze_xid = freeze_xid;
state->rs_cutoff_multi = cutoff_multi;
@@ -327,7 +331,7 @@ end_heap_rewrite(RewriteState state)
/* Write the last page, if any */
if (state->rs_buffer_valid)
{
if (RelationNeedsWAL(state->rs_new_rel))
if (state->rs_use_wal)
log_newpage(&state->rs_new_rel->rd_node,
MAIN_FORKNUM,
state->rs_blockno,
@@ -342,14 +346,18 @@ end_heap_rewrite(RewriteState state)
}
/*
* When we WAL-logged rel pages, we must nonetheless fsync them. The
* If the rel is WAL-logged, must fsync before commit. We use heap_sync
* to ensure that the toast table gets fsync'd too.
*
* It's obvious that we must do this when not WAL-logging. It's less
* obvious that we have to do it even if we did WAL-log the pages. The
* reason is the same as in tablecmds.c's copy_relation_data(): we're
* writing data that's not in shared buffers, and so a CHECKPOINT
* occurring during the rewriteheap operation won't have fsync'd data we
* wrote before the checkpoint.
*/
if (RelationNeedsWAL(state->rs_new_rel))
smgrimmedsync(state->rs_new_rel->rd_smgr, MAIN_FORKNUM);
heap_sync(state->rs_new_rel);
logical_end_heap_rewrite(state);
@@ -647,6 +655,9 @@ raw_heap_insert(RewriteState state, HeapTuple tup)
{
int options = HEAP_INSERT_SKIP_FSM;
if (!state->rs_use_wal)
options |= HEAP_INSERT_SKIP_WAL;
/*
* While rewriting the heap for VACUUM FULL / CLUSTER, make sure data
* for the TOAST table are not logically decoded. The main heap is
@@ -685,7 +696,7 @@ raw_heap_insert(RewriteState state, HeapTuple tup)
/* Doesn't fit, so write out the existing page */
/* XLOG stuff */
if (RelationNeedsWAL(state->rs_new_rel))
if (state->rs_use_wal)
log_newpage(&state->rs_new_rel->rd_node,
MAIN_FORKNUM,
state->rs_blockno,

41
src/backend/access/nbtree/nbtsort.c
View File

@@ -31,6 +31,18 @@
* them. They will need to be re-read into shared buffers on first use after
* the build finishes.
*
* Since the index will never be used unless it is completely built,
* from a crash-recovery point of view there is no need to WAL-log the
* steps of the build. After completing the index build, we can just sync
* the whole file to disk using smgrimmedsync() before exiting this module.
* This can be seen to be sufficient for crash recovery by considering that
* it's effectively equivalent to what would happen if a CHECKPOINT occurred
* just after the index build. However, it is clearly not sufficient if the
* DBA is using the WAL log for PITR or replication purposes, since another
* machine would not be able to reconstruct the index from WAL. Therefore,
* we log the completed index pages to WAL if and only if WAL archiving is
* active.
*
* This code isn't concerned about the FSM at all. The caller is responsible
* for initializing that.
*
@@ -518,7 +530,12 @@ _bt_leafbuild(BTSpool *btspool, BTSpool *btspool2)
wstate.heap = btspool->heap;
wstate.index = btspool->index;
wstate.btws_use_wal = RelationNeedsWAL(wstate.index);
/*
* We need to log index creation in WAL iff WAL archiving/streaming is
* enabled UNLESS the index isn't WAL-logged anyway.
*/
wstate.btws_use_wal = XLogIsNeeded() && RelationNeedsWAL(wstate.index);
/* reserve the metapage */
wstate.btws_pages_alloced = BTREE_METAPAGE + 1;
@@ -1173,15 +1190,21 @@ _bt_load(BTWriteState *wstate, BTSpool *btspool, BTSpool *btspool2)
_bt_uppershutdown(wstate, state);
/*
* When we WAL-logged index pages, we must nonetheless fsync index files.
* Since we're building outside shared buffers, a CHECKPOINT occurring
* during the build has no way to flush the previously written data to
* disk (indeed it won't know the index even exists). A crash later on
* would replay WAL from the checkpoint, therefore it wouldn't replay our
* earlier WAL entries. If we do not fsync those pages here, they might
* still not be on disk when the crash occurs.
* If the index is WAL-logged, we must fsync it down to disk before it's
* safe to commit the transaction. (For a non-WAL-logged index we don't
* care since the index will be uninteresting after a crash anyway.)
*
* It's obvious that we must do this when not WAL-logging the build. It's
* less obvious that we have to do it even if we did WAL-log the index
* pages. The reason is that since we're building outside shared buffers,
* a CHECKPOINT occurring during the build has no way to flush the
* previously written data to disk (indeed it won't know the index even
* exists). A crash later on would replay WAL from the checkpoint,
* therefore it wouldn't replay our earlier WAL entries. If we do not
* fsync those pages here, they might still not be on disk when the crash
* occurs.
*/
if (wstate->btws_use_wal)
if (RelationNeedsWAL(wstate->index))
{
RelationOpenSmgr(wstate->index);
smgrimmedsync(wstate->index->rd_smgr, MAIN_FORKNUM);

6
src/backend/access/rmgrdesc/gistdesc.c
View File

@@ -46,9 +46,6 @@ gist_desc(StringInfo buf, XLogReaderState *record)
break;
case XLOG_GIST_CREATE_INDEX:
break;
case XLOG_GIST_ASSIGN_LSN:
/* No details to write out */
break;
}
}
@@ -68,9 +65,6 @@ gist_identify(uint8 info)
case XLOG_GIST_CREATE_INDEX:
id = "CREATE_INDEX";
break;
case XLOG_GIST_ASSIGN_LSN:
id = "ASSIGN_LSN";
break;
}
return id;

45
src/backend/access/transam/README
View File

@@ -717,38 +717,6 @@ then restart recovery. This is part of the reason for not writing a WAL
entry until we've successfully done the original action.
Skipping WAL for New RelFileNode
--------------------------------
Under wal_level=minimal, if a change modifies a relfilenode that ROLLBACK
would unlink, in-tree access methods write no WAL for that change. Code that
writes WAL without calling RelationNeedsWAL() must check for this case. This
skipping is mandatory. If a WAL-writing change preceded a WAL-skipping change
for the same block, REDO could overwrite the WAL-skipping change. If a
WAL-writing change followed a WAL-skipping change for the same block, a
related problem would arise. When a WAL record contains no full-page image,
REDO expects the page to match its contents from just before record insertion.
A WAL-skipping change may not reach disk at all, violating REDO's expectation
under full_page_writes=off. For any access method, CommitTransaction() writes
and fsyncs affected blocks before recording the commit.
Prefer to do the same in future access methods. However, two other approaches
can work. First, an access method can irreversibly transition a given fork
from WAL-skipping to WAL-writing by calling FlushRelationBuffers() and
smgrimmedsync(). Second, an access method can opt to write WAL
unconditionally for permanent relations. Under these approaches, the access
method callbacks must not call functions that react to RelationNeedsWAL().
This applies only to WAL records whose replay would modify bytes stored in the
new relfilenode. It does not apply to other records about the relfilenode,
such as XLOG_SMGR_CREATE. Because it operates at the level of individual
relfilenodes, RelationNeedsWAL() can differ for tightly-coupled relations.
Consider "CREATE TABLE t (); BEGIN; ALTER TABLE t ADD c text; ..." in which
ALTER TABLE adds a TOAST relation. The TOAST relation will skip WAL, while
the table owning it will not. ALTER TABLE SET TABLESPACE will cause a table
to skip WAL, but that won't affect its indexes.
Asynchronous Commit
-------------------
@@ -852,12 +820,13 @@ Changes to a temp table are not WAL-logged, hence could reach disk in
advance of T1's commit, but we don't care since temp table contents don't
survive crashes anyway.
Database writes that skip WAL for new relfilenodes are also safe. In these
cases it's entirely possible for the data to reach disk before T1's commit,
because T1 will fsync it down to disk without any sort of interlock. However,
all these paths are designed to write data that no other transaction can see
until after T1 commits. The situation is thus not different from ordinary
WAL-logged updates.
Database writes made via any of the paths we have introduced to avoid WAL
overhead for bulk updates are also safe. In these cases it's entirely
possible for the data to reach disk before T1's commit, because T1 will
fsync it down to disk without any sort of interlock, as soon as it finishes
the bulk update. However, all these paths are designed to write data that
no other transaction can see until after T1 commits. The situation is thus
not different from ordinary WAL-logged updates.
Transaction Emulation during Recovery
-------------------------------------

15
src/backend/access/transam/xact.c
View File

@@ -2035,13 +2035,6 @@ CommitTransaction(void)
*/
PreCommit_on_commit_actions();
/*
* Synchronize files that are created and not WAL-logged during this
* transaction. This must happen before AtEOXact_RelationMap(), so that we
* don't see committed-but-broken files after a crash.
*/
smgrDoPendingSyncs(true);
/* close large objects before lower-level cleanup */
AtEOXact_LargeObject(true);
@@ -2271,13 +2264,6 @@ PrepareTransaction(void)
*/
PreCommit_on_commit_actions();
/*
* Synchronize files that are created and not WAL-logged during this
* transaction. This must happen before EndPrepare(), so that we don't see
* committed-but-broken files after a crash and COMMIT PREPARED.
*/
smgrDoPendingSyncs(true);
/* close large objects before lower-level cleanup */
AtEOXact_LargeObject(true);
@@ -2602,7 +2588,6 @@ AbortTransaction(void)
*/
AfterTriggerEndXact(false); /* 'false' means it's abort */
AtAbort_Portals();
smgrDoPendingSyncs(false);
AtEOXact_LargeObject(false);
AtAbort_Notify();
AtEOXact_RelationMap(false);

18
src/backend/access/transam/xlogutils.c
View File

@@ -544,8 +544,6 @@ typedef FakeRelCacheEntryData *FakeRelCacheEntry;
* fields related to physical storage, like rd_rel, are initialized, so the
* fake entry is only usable in low-level operations like ReadBuffer().
*
* This is also used for syncing WAL-skipped files.
*
* Caller must free the returned entry with FreeFakeRelcacheEntry().
*/
Relation
@@ -554,20 +552,18 @@ CreateFakeRelcacheEntry(RelFileNode rnode)
FakeRelCacheEntry fakeentry;
Relation rel;
Assert(InRecovery);
/* Allocate the Relation struct and all related space in one block. */
fakeentry = palloc0(sizeof(FakeRelCacheEntryData));
rel = (Relation) fakeentry;
rel->rd_rel = &fakeentry->pgc;
rel->rd_node = rnode;
/*
* We will never be working with temp rels during recovery or while
* syncing WAL-skipped files.
*/
/* We will never be working with temp rels during recovery */
rel->rd_backend = InvalidBackendId;
/* It must be a permanent table here */
/* It must be a permanent table if we're in recovery. */
rel->rd_rel->relpersistence = RELPERSISTENCE_PERMANENT;
/* We don't know the name of the relation; use relfilenode instead */
@@ -576,9 +572,9 @@ CreateFakeRelcacheEntry(RelFileNode rnode)
/*
* We set up the lockRelId in case anything tries to lock the dummy
* relation. Note that this is fairly bogus since relNode may be
* different from the relation's OID. It shouldn't really matter though.
* In recovery, we are running by ourselves and can't have any lock
* conflicts. While syncing, we already hold AccessExclusiveLock.
* different from the relation's OID. It shouldn't really matter though,
* since we are presumably running by ourselves and can't have any lock
* conflicts ...
*/
rel->rd_lockInfo.lockRelId.dbId = rnode.dbNode;
rel->rd_lockInfo.lockRelId.relId = rnode.relNode;