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Code Activity

Clean up manipulations of hash indexes' hasho_flag field.

Browse Source 
Standardize on testing a hash index page's type by doing
	(opaque->hasho_flag & LH_PAGE_TYPE) == LH_xxx_PAGE
Various places were taking shortcuts like
	opaque->hasho_flag & LH_BUCKET_PAGE
which while not actually wrong, is still bad practice because
it encourages use of
	opaque->hasho_flag & LH_UNUSED_PAGE
which *is* wrong (LH_UNUSED_PAGE == 0, so the above is constant false).
hash_xlog.c's hash_mask() contained such an incorrect test.

This also ensures that we mask out the additional flag bits that
hasho_flag has accreted since 9.6.  pgstattuple's pgstat_hash_page(),
for one, was failing to do that and was thus actively broken.

Also fix assorted comments that hadn't been updated to reflect the
extended usage of hasho_flag, and fix some macros that were testing
just "(hasho_flag & bit)" to use the less dangerous, project-approved
form "((hasho_flag & bit) != 0)".

Coverity found the bug in hash_mask(); I noted the one in
pgstat_hash_page() through code reading.
This commit is contained in:
Tom Lane
2017-04-14 17:04:25 -04:00
parent 1dffabed49
commit 2040bb4a0b
6 changed files with 29 additions and 25 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
src/backend/access/hash/hash_xlog.c
View File

@@ -1234,6 +1234,7 @@ hash_mask(char *pagedata, BlockNumber blkno)
{
Page page = (Page) pagedata;
HashPageOpaque opaque;
int pagetype;
mask_page_lsn(page);
@@ -1242,15 +1243,16 @@ hash_mask(char *pagedata, BlockNumber blkno)
opaque = (HashPageOpaque) PageGetSpecialPointer(page);
if (opaque->hasho_flag & LH_UNUSED_PAGE)
pagetype = opaque->hasho_flag & LH_PAGE_TYPE;
if (pagetype == LH_UNUSED_PAGE)
{
/*
* Mask everything on a UNUSED page.
*/
mask_page_content(page);
}
else if ((opaque->hasho_flag & LH_BUCKET_PAGE) ||
(opaque->hasho_flag & LH_OVERFLOW_PAGE))
else if (pagetype == LH_BUCKET_PAGE ||
pagetype == LH_OVERFLOW_PAGE)
{
/*
* In hash bucket and overflow pages, it is possible to modify the

2
src/backend/access/hash/hashovfl.c
View File

@@ -168,7 +168,7 @@ _hash_addovflpage(Relation rel, Buffer metabuf, Buffer buf, bool retain_pin)
if (retain_pin)
{
/* pin will be retained only for the primary bucket page */
Assert(pageopaque->hasho_flag & LH_BUCKET_PAGE);
Assert((pageopaque->hasho_flag & LH_PAGE_TYPE) == LH_BUCKET_PAGE);
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
}
else

4
src/backend/access/hash/hashutil.c
View File

@@ -218,8 +218,8 @@ _hash_get_totalbuckets(uint32 splitpoint_phase)
/*
* _hash_checkpage -- sanity checks on the format of all hash pages
*
* If flags is not zero, it is a bitwise OR of the acceptable values of
* hasho_flag.
* If flags is not zero, it is a bitwise OR of the acceptable page types
* (values of hasho_flag & LH_PAGE_TYPE).
*/
void
_hash_checkpage(Relation rel, Buffer buf, int flags)