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There's a project policy against using plain "char buf[BLCKSZ]" local or static variables as page buffers; preferred style is to palloc or malloc each buffer to ensure it is MAXALIGN'd. However, that policy's been ignored in an increasing number of places. We've apparently got away with it so far, probably because (a) relatively few people use platforms on which misalignment causes core dumps and/or (b) the variables chance to be sufficiently aligned anyway. But this is not something to rely on. Moreover, even if we don't get a core dump, we might be paying a lot of cycles for misaligned accesses. To fix, invent new union types PGAlignedBlock and PGAlignedXLogBlock that the compiler must allocate with sufficient alignment, and use those in place of plain char arrays. I used these types even for variables where there's no risk of a misaligned access, since ensuring proper alignment should make kernel data transfers faster. I also changed some places where we had been palloc'ing short-lived buffers, for coding style uniformity and to save palloc/pfree overhead. Since this seems to be a live portability hazard (despite the lack of field reports), back-patch to all supported versions. Patch by me; thanks to Michael Paquier for review. Discussion: https://postgr.es/m/1535618100.1286.3.camel@credativ.de
364 lines
9.6 KiB
C
364 lines
9.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* blinsert.c
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* Bloom index build and insert functions.
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*
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* Copyright (c) 2016, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* contrib/bloom/blinsert.c
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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/genam.h"
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#include "access/generic_xlog.h"
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#include "catalog/index.h"
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#include "miscadmin.h"
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#include "storage/bufmgr.h"
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#include "storage/indexfsm.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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#include "bloom.h"
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PG_MODULE_MAGIC;
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/*
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* State of bloom index build. We accumulate one page data here before
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* flushing it to buffer manager.
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*/
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typedef struct
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{
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BloomState blstate; /* bloom index state */
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int64 indtuples; /* total number of tuples indexed */
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MemoryContext tmpCtx; /* temporary memory context reset after each
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* tuple */
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PGAlignedBlock data; /* cached page */
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int count; /* number of tuples in cached page */
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} BloomBuildState;
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/*
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* Flush page cached in BloomBuildState.
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*/
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static void
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flushCachedPage(Relation index, BloomBuildState *buildstate)
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{
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Page page;
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Buffer buffer = BloomNewBuffer(index);
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GenericXLogState *state;
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state = GenericXLogStart(index);
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page = GenericXLogRegisterBuffer(state, buffer, GENERIC_XLOG_FULL_IMAGE);
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memcpy(page, buildstate->data.data, BLCKSZ);
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GenericXLogFinish(state);
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UnlockReleaseBuffer(buffer);
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}
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/*
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* (Re)initialize cached page in BloomBuildState.
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*/
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static void
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initCachedPage(BloomBuildState *buildstate)
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{
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memset(buildstate->data.data, 0, BLCKSZ);
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BloomInitPage(buildstate->data.data, 0);
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buildstate->count = 0;
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}
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/*
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* Per-tuple callback from IndexBuildHeapScan.
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*/
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static void
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bloomBuildCallback(Relation index, HeapTuple htup, Datum *values,
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bool *isnull, bool tupleIsAlive, void *state)
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{
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BloomBuildState *buildstate = (BloomBuildState *) state;
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MemoryContext oldCtx;
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BloomTuple *itup;
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oldCtx = MemoryContextSwitchTo(buildstate->tmpCtx);
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itup = BloomFormTuple(&buildstate->blstate, &htup->t_self, values, isnull);
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/* Try to add next item to cached page */
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if (BloomPageAddItem(&buildstate->blstate, buildstate->data.data, itup))
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{
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/* Next item was added successfully */
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buildstate->count++;
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}
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else
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{
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/* Cached page is full, flush it out and make a new one */
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flushCachedPage(index, buildstate);
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CHECK_FOR_INTERRUPTS();
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initCachedPage(buildstate);
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if (!BloomPageAddItem(&buildstate->blstate, buildstate->data.data, itup))
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{
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/* We shouldn't be here since we're inserting to the empty page */
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elog(ERROR, "could not add new bloom tuple to empty page");
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}
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/* Next item was added successfully */
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buildstate->count++;
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}
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/* Update total tuple count */
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buildstate->indtuples += 1;
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MemoryContextSwitchTo(oldCtx);
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MemoryContextReset(buildstate->tmpCtx);
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}
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/*
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* Build a new bloom index.
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*/
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IndexBuildResult *
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blbuild(Relation heap, Relation index, IndexInfo *indexInfo)
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{
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IndexBuildResult *result;
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double reltuples;
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BloomBuildState buildstate;
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if (RelationGetNumberOfBlocks(index) != 0)
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elog(ERROR, "index \"%s\" already contains data",
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RelationGetRelationName(index));
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/* Initialize the meta page */
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BloomInitMetapage(index);
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/* Initialize the bloom build state */
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memset(&buildstate, 0, sizeof(buildstate));
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initBloomState(&buildstate.blstate, index);
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buildstate.tmpCtx = AllocSetContextCreate(CurrentMemoryContext,
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"Bloom build temporary context",
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ALLOCSET_DEFAULT_SIZES);
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initCachedPage(&buildstate);
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/* Do the heap scan */
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reltuples = IndexBuildHeapScan(heap, index, indexInfo, true,
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bloomBuildCallback, (void *) &buildstate);
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/* Flush last page if needed (it will be, unless heap was empty) */
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if (buildstate.count > 0)
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flushCachedPage(index, &buildstate);
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MemoryContextDelete(buildstate.tmpCtx);
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result = (IndexBuildResult *) palloc(sizeof(IndexBuildResult));
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result->heap_tuples = reltuples;
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result->index_tuples = buildstate.indtuples;
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return result;
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}
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/*
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* Build an empty bloom index in the initialization fork.
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*/
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void
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blbuildempty(Relation index)
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{
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Page metapage;
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/* Construct metapage. */
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metapage = (Page) palloc(BLCKSZ);
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BloomFillMetapage(index, metapage);
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/*
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* Write the page and log it. It might seem that an immediate sync
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* would be sufficient to guarantee that the file exists on disk, but
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* recovery itself might remove it while replaying, for example, an
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* XLOG_DBASE_CREATE or XLOG_TBLSPC_CREATE record. Therefore, we
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* need this even when wal_level=minimal.
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*/
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PageSetChecksumInplace(metapage, BLOOM_METAPAGE_BLKNO);
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smgrwrite(index->rd_smgr, INIT_FORKNUM, BLOOM_METAPAGE_BLKNO,
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(char *) metapage, true);
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log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
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BLOOM_METAPAGE_BLKNO, metapage, false);
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/*
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* An immediate sync is required even if we xlog'd the page, because the
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* write did not go through shared_buffers and therefore a concurrent
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* checkpoint may have moved the redo pointer past our xlog record.
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*/
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smgrimmedsync(index->rd_smgr, INIT_FORKNUM);
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}
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/*
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* Insert new tuple to the bloom index.
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*/
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bool
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blinsert(Relation index, Datum *values, bool *isnull,
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ItemPointer ht_ctid, Relation heapRel, IndexUniqueCheck checkUnique)
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{
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BloomState blstate;
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BloomTuple *itup;
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MemoryContext oldCtx;
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MemoryContext insertCtx;
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BloomMetaPageData *metaData;
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Buffer buffer,
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metaBuffer;
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Page page,
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metaPage;
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BlockNumber blkno = InvalidBlockNumber;
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OffsetNumber nStart;
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GenericXLogState *state;
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insertCtx = AllocSetContextCreate(CurrentMemoryContext,
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"Bloom insert temporary context",
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ALLOCSET_DEFAULT_SIZES);
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oldCtx = MemoryContextSwitchTo(insertCtx);
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initBloomState(&blstate, index);
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itup = BloomFormTuple(&blstate, ht_ctid, values, isnull);
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/*
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* At first, try to insert new tuple to the first page in notFullPage
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* array. If successful, we don't need to modify the meta page.
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*/
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metaBuffer = ReadBuffer(index, BLOOM_METAPAGE_BLKNO);
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LockBuffer(metaBuffer, BUFFER_LOCK_SHARE);
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metaData = BloomPageGetMeta(BufferGetPage(metaBuffer));
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if (metaData->nEnd > metaData->nStart)
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{
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Page page;
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blkno = metaData->notFullPage[metaData->nStart];
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Assert(blkno != InvalidBlockNumber);
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/* Don't hold metabuffer lock while doing insert */
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LockBuffer(metaBuffer, BUFFER_LOCK_UNLOCK);
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buffer = ReadBuffer(index, blkno);
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LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
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state = GenericXLogStart(index);
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page = GenericXLogRegisterBuffer(state, buffer, 0);
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/*
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* We might have found a page that was recently deleted by VACUUM. If
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* so, we can reuse it, but we must reinitialize it.
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*/
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if (PageIsNew(page) || BloomPageIsDeleted(page))
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BloomInitPage(page, 0);
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if (BloomPageAddItem(&blstate, page, itup))
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{
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/* Success! Apply the change, clean up, and exit */
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GenericXLogFinish(state);
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UnlockReleaseBuffer(buffer);
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ReleaseBuffer(metaBuffer);
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MemoryContextSwitchTo(oldCtx);
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MemoryContextDelete(insertCtx);
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return false;
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}
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/* Didn't fit, must try other pages */
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GenericXLogAbort(state);
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UnlockReleaseBuffer(buffer);
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}
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else
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{
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/* No entries in notFullPage */
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LockBuffer(metaBuffer, BUFFER_LOCK_UNLOCK);
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}
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/*
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* Try other pages in notFullPage array. We will have to change nStart in
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* metapage. Thus, grab exclusive lock on metapage.
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*/
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LockBuffer(metaBuffer, BUFFER_LOCK_EXCLUSIVE);
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/* nStart might have changed while we didn't have lock */
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nStart = metaData->nStart;
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/* Skip first page if we already tried it above */
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if (nStart < metaData->nEnd &&
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blkno == metaData->notFullPage[nStart])
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nStart++;
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/*
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* This loop iterates for each page we try from the notFullPage array, and
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* will also initialize a GenericXLogState for the fallback case of having
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* to allocate a new page.
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*/
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for (;;)
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{
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state = GenericXLogStart(index);
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/* get modifiable copy of metapage */
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metaPage = GenericXLogRegisterBuffer(state, metaBuffer, 0);
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metaData = BloomPageGetMeta(metaPage);
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if (nStart >= metaData->nEnd)
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break; /* no more entries in notFullPage array */
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blkno = metaData->notFullPage[nStart];
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Assert(blkno != InvalidBlockNumber);
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buffer = ReadBuffer(index, blkno);
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LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
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page = GenericXLogRegisterBuffer(state, buffer, 0);
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/* Basically same logic as above */
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if (PageIsNew(page) || BloomPageIsDeleted(page))
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BloomInitPage(page, 0);
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if (BloomPageAddItem(&blstate, page, itup))
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{
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/* Success! Apply the changes, clean up, and exit */
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metaData->nStart = nStart;
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GenericXLogFinish(state);
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UnlockReleaseBuffer(buffer);
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UnlockReleaseBuffer(metaBuffer);
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MemoryContextSwitchTo(oldCtx);
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MemoryContextDelete(insertCtx);
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return false;
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}
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/* Didn't fit, must try other pages */
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GenericXLogAbort(state);
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UnlockReleaseBuffer(buffer);
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nStart++;
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}
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/*
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* Didn't find place to insert in notFullPage array. Allocate new page.
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* (XXX is it good to do this while holding ex-lock on the metapage??)
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*/
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buffer = BloomNewBuffer(index);
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page = GenericXLogRegisterBuffer(state, buffer, GENERIC_XLOG_FULL_IMAGE);
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BloomInitPage(page, 0);
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if (!BloomPageAddItem(&blstate, page, itup))
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{
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/* We shouldn't be here since we're inserting to an empty page */
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elog(ERROR, "could not add new bloom tuple to empty page");
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}
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/* Reset notFullPage array to contain just this new page */
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metaData->nStart = 0;
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metaData->nEnd = 1;
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metaData->notFullPage[0] = BufferGetBlockNumber(buffer);
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/* Apply the changes, clean up, and exit */
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GenericXLogFinish(state);
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UnlockReleaseBuffer(buffer);
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UnlockReleaseBuffer(metaBuffer);
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MemoryContextSwitchTo(oldCtx);
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MemoryContextDelete(insertCtx);
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return false;
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}
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