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| author | Peter Geoghegan <pg@bowt.ie> | 2022-01-12 15:41:04 -0800 |
|---|---|---|
| committer | Peter Geoghegan <pg@bowt.ie> | 2022-01-12 15:41:04 -0800 |
| commit | db6736c93cb844d245b726e7a262f2cdcd34612e (patch) | |
| tree | 9b564faefa8291948815d793bab0dbf78f95c7d5 /src/include/nodes/execnodes.h | |
| parent | e9b873f667681232469007d755d0c163a63ea978 (diff) | |
| download | postgresql-db6736c93cb844d245b726e7a262f2cdcd34612e.tar.gz postgresql-db6736c93cb844d245b726e7a262f2cdcd34612e.zip | |
Fix memory leak in indexUnchanged hint mechanism.
Commit 9dc718bd added a "logically unchanged by UPDATE" hinting
mechanism, which is currently used within nbtree indexes only (see
commit d168b666). This mechanism determined whether or not the incoming
item is a logically unchanged duplicate (a duplicate needed only for
MVCC versioning purposes) once per row updated per non-HOT update. This
approach led to memory leaks which were noticeable with an UPDATE
statement that updated sufficiently many rows, at least on tables that
happen to have an expression index.
On HEAD, fix the issue by adding a cache to the executor's per-index
IndexInfo struct.
Take a different approach on Postgres 14 to avoid an ABI break: simply
pass down the hint to all indexes unconditionally with non-HOT UPDATEs.
This is deemed acceptable because the hint is currently interpreted
within btinsert() as "perform a bottom-up index deletion pass if and
when the only alternative is splitting the leaf page -- prefer to delete
any LP_DEAD-set items first". nbtree must always treat the hint as a
noisy signal about what might work, as a strategy of last resort, with
costs imposed on non-HOT updaters. (The same thing might not be true
within another index AM that applies the hint, which is why the original
behavior is preserved on HEAD.)
Author: Peter Geoghegan <pg@bowt.ie>
Reported-By: Klaudie Willis <Klaudie.Willis@protonmail.com>
Diagnosed-By: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/261065.1639497535@sss.pgh.pa.us
Backpatch: 14-, where the hinting mechanism was added.
Diffstat (limited to 'src/include/nodes/execnodes.h')
| -rw-r--r-- | src/include/nodes/execnodes.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h index 8429a9c55df..4ea8735dd81 100644 --- a/src/include/nodes/execnodes.h +++ b/src/include/nodes/execnodes.h @@ -142,6 +142,8 @@ typedef struct ExprState * Unique is it a unique index? * OpclassOptions opclass-specific options, or NULL if none * ReadyForInserts is it valid for inserts? + * CheckedUnchanged IndexUnchanged status determined yet? + * IndexUnchanged aminsert hint, cached for retail inserts * Concurrent are we doing a concurrent index build? * BrokenHotChain did we detect any broken HOT chains? * ParallelWorkers # of workers requested (excludes leader) @@ -172,6 +174,8 @@ typedef struct IndexInfo Datum *ii_OpclassOptions; /* array with one entry per column */ bool ii_Unique; bool ii_ReadyForInserts; + bool ii_CheckedUnchanged; + bool ii_IndexUnchanged; bool ii_Concurrent; bool ii_BrokenHotChain; int ii_ParallelWorkers; |