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2015年7月21日 17:38:24 +0000 (13:38 -0400)

Remove HeapScanDescData.rs_initblock, which wasn't being used for anything
in the final version of the patch.

Fix IndexBuildHeapScan so that it supports syncscan again; the patch
broke synchronous scanning for index builds by forcing rs_startblk
to zero even when the caller did not care about that and had asked
for syncscan.

Add some commentary and usage defenses to heap_setscanlimits().

Fix heapam so that asking for rs_numblocks == 0 does what you would
reasonably expect. As coded it amounted to requesting a whole-table
scan, because those "--x <= 0" tests on an unsigned variable would
behave surprisingly.

src/backend/access/heap/heapam.c patch | blob | blame | history

src/backend/catalog/index.c patch | blob | blame | history

src/include/access/relscan.h patch | blob | blame | history

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c

index 86a2e6bae6abdb5fdc62f1a2078f645111abc8a4..6f4ff2718fed8d224837d2aeb46da44cb5cadecd 100644 (file)

--- a/src/backend/access/heap/heapam.c

+++ b/src/backend/access/heap/heapam.c

@@ -277,7 +277,6 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)

scan->rs_startblock = 0;

}

- scan->rs_initblock = 0;

scan->rs_numblocks = InvalidBlockNumber;

scan->rs_inited = false;

scan->rs_ctup.t_data = NULL;

@@ -302,11 +301,22 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)

pgstat_count_heap_scan(scan->rs_rd);

}

+/*

+ * heap_setscanlimits - restrict range of a heapscan

+ *

+ * startBlk is the page to start at

+ * numBlks is number of pages to scan (InvalidBlockNumber means "all")

+ */

void

heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk, BlockNumber numBlks)

{

+ Assert(!scan->rs_inited); /* else too late to change */

+ Assert(!scan->rs_syncscan); /* else rs_startblock is significant */

+ /* Check startBlk is valid (but allow case of zero blocks...) */

+ Assert(startBlk == 0 || startBlk < scan->rs_nblocks);

scan->rs_startblock = startBlk;

- scan->rs_initblock = startBlk;

scan->rs_numblocks = numBlks;

}

@@ -477,7 +487,7 @@ heapgettup(HeapScanDesc scan,

* return null immediately if relation is empty

- if (scan->rs_nblocks == 0)

+ if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0)

{

Assert(!BufferIsValid(scan->rs_cbuf));

tuple->t_data = NULL;

@@ -511,7 +521,7 @@ heapgettup(HeapScanDesc scan,

* return null immediately if relation is empty

- if (scan->rs_nblocks == 0)

+ if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0)

{

Assert(!BufferIsValid(scan->rs_cbuf));

tuple->t_data = NULL;

@@ -651,7 +661,7 @@ heapgettup(HeapScanDesc scan,

if (backward)

{

finished = (page == scan->rs_startblock) ||

- (scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks <= 0 : false);

+ (scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks == 0 : false);

if (page == 0)

page = scan->rs_nblocks;

page--;

@@ -662,7 +672,7 @@ heapgettup(HeapScanDesc scan,

if (page >= scan->rs_nblocks)

page = 0;

finished = (page == scan->rs_startblock) ||

- (scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks <= 0 : false);

+ (scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks == 0 : false);

* Report our new scan position for synchronization purposes. We

@@ -754,7 +764,7 @@ heapgettup_pagemode(HeapScanDesc scan,

* return null immediately if relation is empty

- if (scan->rs_nblocks == 0)

+ if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0)

{

Assert(!BufferIsValid(scan->rs_cbuf));

tuple->t_data = NULL;

@@ -785,7 +795,7 @@ heapgettup_pagemode(HeapScanDesc scan,

* return null immediately if relation is empty

- if (scan->rs_nblocks == 0)

+ if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0)

{

Assert(!BufferIsValid(scan->rs_cbuf));

tuple->t_data = NULL;

@@ -914,7 +924,7 @@ heapgettup_pagemode(HeapScanDesc scan,

if (backward)

{

finished = (page == scan->rs_startblock) ||

- (scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks <= 0 : false);

+ (scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks == 0 : false);

if (page == 0)

page = scan->rs_nblocks;

page--;

@@ -925,7 +935,7 @@ heapgettup_pagemode(HeapScanDesc scan,

if (page >= scan->rs_nblocks)

page = 0;

finished = (page == scan->rs_startblock) ||

- (scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks <= 0 : false);

+ (scan->rs_numblocks != InvalidBlockNumber ? --scan->rs_numblocks == 0 : false);

* Report our new scan position for synchronization purposes. We

diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c

index 4246554d19d21fb5da4c6369f24d71c86b6c5059..69f35c933097920c3a0da919e8a9ef7ff6563fec 100644 (file)

--- a/src/backend/catalog/index.c

+++ b/src/backend/catalog/index.c

@@ -2168,7 +2168,8 @@ IndexBuildHeapScan(Relation heapRelation,

* As above, except that instead of scanning the complete heap, only the given

* number of blocks are scanned. Scan to end-of-rel can be signalled by

- * passing InvalidBlockNumber as numblocks.

+ * passing InvalidBlockNumber as numblocks. Note that restricting the range

+ * to scan cannot be done when requesting syncscan.

double

IndexBuildHeapRangeScan(Relation heapRelation,

@@ -2251,7 +2252,14 @@ IndexBuildHeapRangeScan(Relation heapRelation,

allow_sync); /* syncscan OK? */

/* set our scan endpoints */

- heap_setscanlimits(scan, start_blockno, numblocks);

+ if (!allow_sync)

+ heap_setscanlimits(scan, start_blockno, numblocks);

+ else

+ {

+ /* syncscan can only be requested on whole relation */

+ Assert(start_blockno == 0);

+ Assert(numblocks == InvalidBlockNumber);

+ }

reltuples = 0;

diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h

index f2482e99d6c56e12eec3ba97b65766ce59c5291e..6e6231971fdca3ef0a780f179b7cda515b4835a3 100644 (file)

--- a/src/include/access/relscan.h

+++ b/src/include/access/relscan.h

@@ -38,8 +38,8 @@ typedef struct HeapScanDescData

/* state set up at initscan time */

BlockNumber rs_nblocks; /* total number of blocks in rel */

BlockNumber rs_startblock; /* block # to start at */

- BlockNumber rs_initblock; /* block # to consider initial of rel */

- BlockNumber rs_numblocks; /* number of blocks to scan */

+ BlockNumber rs_numblocks; /* max number of blocks to scan */

+ /* rs_numblocks is usually InvalidBlockNumber, meaning "scan whole rel" */

BufferAccessStrategy rs_strategy; /* access strategy for reads */

bool rs_syncscan; /* report location to syncscan logic? */

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