Fix incorrect loop counts in tidbitmap.c.

tglsfdc · tglsfdc · commit 6765a2c96af4 · 2013-11-15T18:34:39.000-05:00
A couple of places that should have been iterating over WORDS_PER_CHUNK
words were iterating over WORDS_PER_PAGE words instead.  This thinko
accidentally failed to fail, because (at least on common architectures
with default BLCKSZ) WORDS_PER_CHUNK is a bit less than WORDS_PER_PAGE,
and the extra words being looked at were always zero so nothing happened.
Still, it's a bug waiting to happen if anybody ever fools with the
parameters affecting TIDBitmap sizes, and it's a small waste of cycles
too.  So back-patch to all active branches.

Etsuro Fujita
diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
@@ -362,7 +362,7 @@ tbm_union_page(TIDBitmap *a, const PagetableEntry *bpage)
 	if (bpage->ischunk)
 	{
 		/* Scan b's chunk, mark each indicated page lossy in a */
-		for (wordnum = 0; wordnum < WORDS_PER_PAGE; wordnum++)
+		for (wordnum = 0; wordnum < WORDS_PER_CHUNK; wordnum++)
 		{
 			bitmapword	w = bpage->words[wordnum];
 
@@ -474,7 +474,7 @@ tbm_intersect_page(TIDBitmap *a, PagetableEntry *apage, const TIDBitmap *b)
 		/* Scan each bit in chunk, try to clear */
 		bool		candelete = true;
 
-		for (wordnum = 0; wordnum < WORDS_PER_PAGE; wordnum++)
+		for (wordnum = 0; wordnum < WORDS_PER_CHUNK; wordnum++)
 		{
 			bitmapword	w = apage->words[wordnum];
 

Original file line number	Diff line number	Diff line change
`@@ -362,7 +362,7 @@ tbm_union_page(TIDBitmap a, const PagetableEntry bpage)`
`362`	`362`	`if (bpage->ischunk)`
`363`	`363`	`{`
`364`	`364`	`/* Scan b's chunk, mark each indicated page lossy in a */`
`365`		`- for (wordnum = 0; wordnum < WORDS_PER_PAGE; wordnum++)`
	`365`	`+ for (wordnum = 0; wordnum < WORDS_PER_CHUNK; wordnum++)`
`366`	`366`	`{`
`367`	`367`	`bitmapword w = bpage->words[wordnum];`
`368`	`368`
`@@ -474,7 +474,7 @@ tbm_intersect_page(TIDBitmap a, PagetableEntry apage, const TIDBitmap *b)`
`474`	`474`	`/* Scan each bit in chunk, try to clear */`
`475`	`475`	`bool candelete = true;`
`476`	`476`
`477`		`- for (wordnum = 0; wordnum < WORDS_PER_PAGE; wordnum++)`
	`477`	`+ for (wordnum = 0; wordnum < WORDS_PER_CHUNK; wordnum++)`
`478`	`478`	`{`
`479`	`479`	`bitmapword w = apage->words[wordnum];`
`480`	`480`