From 2040bb4a0b50ef0434a1a723f00d040ab4f1c06f Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 14 Apr 2017 17:04:25 -0400
Subject: [PATCH] Clean up manipulations of hash indexes' hasho_flag field.
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.
---
contrib/pageinspect/hashfuncs.c | 12 +++++++-----
contrib/pgstattuple/pgstattuple.c | 2 +-
src/backend/access/hash/hash_xlog.c | 8 +++++---
src/backend/access/hash/hashovfl.c | 2 +-
src/backend/access/hash/hashutil.c | 4 ++--
src/include/access/hash.h | 26 +++++++++++++-------------
6 files changed, 29 insertions(+), 25 deletions(-)
diff --git a/contrib/pageinspect/hashfuncs.c b/contrib/pageinspect/hashfuncs.c
index dd00aaa81a..6e52969fd3 100644
--- a/contrib/pageinspect/hashfuncs.c
+++ b/contrib/pageinspect/hashfuncs.c
@@ -184,7 +184,8 @@ hash_page_type(PG_FUNCTION_ARGS)
bytea *raw_page = PG_GETARG_BYTEA_P(0);
Page page;
HashPageOpaque opaque;
- char *type;
+ int pagetype;
+ const char *type;
if (!superuser())
ereport(ERROR,
@@ -200,13 +201,14 @@ hash_page_type(PG_FUNCTION_ARGS)
opaque = (HashPageOpaque) PageGetSpecialPointer(page);
/* page type (flags) */
- if (opaque->hasho_flag & LH_META_PAGE)
+ pagetype = opaque->hasho_flag & LH_PAGE_TYPE;
+ if (pagetype == LH_META_PAGE)
type = "metapage";
- else if (opaque->hasho_flag & LH_OVERFLOW_PAGE)
+ else if (pagetype == LH_OVERFLOW_PAGE)
type = "overflow";
- else if (opaque->hasho_flag & LH_BUCKET_PAGE)
+ else if (pagetype == LH_BUCKET_PAGE)
type = "bucket";
- else if (opaque->hasho_flag & LH_BITMAP_PAGE)
+ else if (pagetype == LH_BITMAP_PAGE)
type = "bitmap";
else
type = "unused";
diff --git a/contrib/pgstattuple/pgstattuple.c b/contrib/pgstattuple/pgstattuple.c
index 44f90cd0d3..eb02ec5b89 100644
--- a/contrib/pgstattuple/pgstattuple.c
+++ b/contrib/pgstattuple/pgstattuple.c
@@ -453,7 +453,7 @@ pgstat_hash_page(pgstattuple_type *stat, Relation rel, BlockNumber blkno,
HashPageOpaque opaque;
opaque = (HashPageOpaque) PageGetSpecialPointer(page);
- switch (opaque->hasho_flag)
+ switch (opaque->hasho_flag & LH_PAGE_TYPE)
{
case LH_UNUSED_PAGE:
stat->free_space += BLCKSZ;
diff --git a/src/backend/access/hash/hash_xlog.c b/src/backend/access/hash/hash_xlog.c
index 2ccaf469e7..d1c0e6904f 100644
--- a/src/backend/access/hash/hash_xlog.c
+++ b/src/backend/access/hash/hash_xlog.c
@@ -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
diff --git a/src/backend/access/hash/hashovfl.c b/src/backend/access/hash/hashovfl.c
index d5f5023068..b5133e3945 100644
--- a/src/backend/access/hash/hashovfl.c
+++ b/src/backend/access/hash/hashovfl.c
@@ -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
diff --git a/src/backend/access/hash/hashutil.c b/src/backend/access/hash/hashutil.c
index 037582bd79..9f832f2544 100644
--- a/src/backend/access/hash/hashutil.c
+++ b/src/backend/access/hash/hashutil.c
@@ -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)
diff --git a/src/include/access/hash.h b/src/include/access/hash.h
index fcc3957036..adba224008 100644
--- a/src/include/access/hash.h
+++ b/src/include/access/hash.h
@@ -41,13 +41,13 @@ typedef uint32 Bucket;
/*
* Special space for hash index pages.
*
- * hasho_flag tells us which type of page we're looking at. For
- * example, knowing overflow pages from bucket pages is necessary
- * information when you're deleting tuples from a page. If all the
- * tuples are deleted from an overflow page, the overflow is made
- * available to other buckets by calling _hash_freeovflpage(). If all
- * the tuples are deleted from a bucket page, no additional action is
- * necessary.
+ * hasho_flag's LH_PAGE_TYPE bits tell us which type of page we're looking at.
+ * Additional bits in the flag word are used for more transient purposes.
+ *
+ * To test a page's type, do (hasho_flag & LH_PAGE_TYPE) == LH_xxx_PAGE.
+ * However, we ensure that each used page type has a distinct bit so that
+ * we can OR together page types for uses such as the allowable-page-types
+ * argument of _hash_checkpage().
*/
#define LH_UNUSED_PAGE (0)
#define LH_OVERFLOW_PAGE (1 << 0)
@@ -60,7 +60,7 @@ typedef uint32 Bucket;
#define LH_PAGE_HAS_DEAD_TUPLES (1 << 7)
#define LH_PAGE_TYPE \
- (LH_OVERFLOW_PAGE|LH_BUCKET_PAGE|LH_BITMAP_PAGE|LH_META_PAGE)
+ (LH_OVERFLOW_PAGE | LH_BUCKET_PAGE | LH_BITMAP_PAGE | LH_META_PAGE)
/*
* In an overflow page, hasho_prevblkno stores the block number of the previous
@@ -78,16 +78,16 @@ typedef struct HashPageOpaqueData
BlockNumber hasho_prevblkno; /* see above */
BlockNumber hasho_nextblkno; /* see above */
Bucket hasho_bucket; /* bucket number this pg belongs to */
- uint16 hasho_flag; /* page type code, see above */
+ uint16 hasho_flag; /* page type code + flag bits, see above */
uint16 hasho_page_id; /* for identification of hash indexes */
} HashPageOpaqueData;
typedef HashPageOpaqueData *HashPageOpaque;
-#define H_NEEDS_SPLIT_CLEANUP(opaque) ((opaque)->hasho_flag & LH_BUCKET_NEEDS_SPLIT_CLEANUP)
-#define H_BUCKET_BEING_SPLIT(opaque) ((opaque)->hasho_flag & LH_BUCKET_BEING_SPLIT)
-#define H_BUCKET_BEING_POPULATED(opaque) ((opaque)->hasho_flag & LH_BUCKET_BEING_POPULATED)
-#define H_HAS_DEAD_TUPLES(opaque) ((opaque)->hasho_flag & LH_PAGE_HAS_DEAD_TUPLES)
+#define H_NEEDS_SPLIT_CLEANUP(opaque) (((opaque)->hasho_flag & LH_BUCKET_NEEDS_SPLIT_CLEANUP) != 0)
+#define H_BUCKET_BEING_SPLIT(opaque) (((opaque)->hasho_flag & LH_BUCKET_BEING_SPLIT) != 0)
+#define H_BUCKET_BEING_POPULATED(opaque) (((opaque)->hasho_flag & LH_BUCKET_BEING_POPULATED) != 0)
+#define H_HAS_DEAD_TUPLES(opaque) (((opaque)->hasho_flag & LH_PAGE_HAS_DEAD_TUPLES) != 0)
/*
* The page ID is for the convenience of pg_filedump and similar utilities,
--
2.50.1