diff options
| author | Peter Geoghegan | 2025-12-08 18:48:09 +0000 |
|---|---|---|
| committer | Peter Geoghegan | 2025-12-08 18:48:09 +0000 |
| commit | 83a26ba59b1819cbd61705a3ff6aa572081ccc4b (patch) | |
| tree | ab9e0358d80b4baf660dd8c76123237c636577ce | |
| parent | d0d0ba6cf66c4043501f6f7bf508ad920645e415 (diff) | |
Avoid pointer chasing in _bt_readpage inner loop.
Make _bt_readpage pass down the current scan direction to various
utility functions within its pstate variable. Also have _bt_readpage
work off of a local copy of scan->ignore_killed_tuples within its
per-tuple loop (rather than using scan->ignore_killed_tuples directly).
Testing has shown that this significantly benefits large range scans,
which are naturally able to take full advantage of the pstate.startikey
optimization added by commit 8a510275. Running a pgbench script with a
"SELECT abalance FROM pgbench_accounts WHERE aid BETWEEN ..." query
shows an increase in transaction throughput of over 5%. There also
appears to be a small performance benefit when running pgbench's
built-in select-only script.
Follow-up to commit 65d6acbc.
Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Victor Yegorov <vyegorov@gmail.com>
Discussion: https://postgr.es/m/CAH2-WzmwMwcwKFgaf+mYPwiz3iL4AqpXnwtW_O0vqpWPXRom9Q@mail.gmail.com
| -rw-r--r-- | src/backend/access/nbtree/nbtreadpage.c | 19 |
1 files changed, 10 insertions, 9 deletions
diff --git a/src/backend/access/nbtree/nbtreadpage.c b/src/backend/access/nbtree/nbtreadpage.c index 00df52b81be..ac67b6f7a34 100644 --- a/src/backend/access/nbtree/nbtreadpage.c +++ b/src/backend/access/nbtree/nbtreadpage.c @@ -31,6 +31,7 @@ typedef struct BTReadPageState { /* Input parameters, set by _bt_readpage for _bt_checkkeys */ + ScanDirection dir; /* current scan direction */ OffsetNumber minoff; /* Lowest non-pivot tuple's offset */ OffsetNumber maxoff; /* Highest non-pivot tuple's offset */ IndexTuple finaltup; /* Needed by scans with array keys */ @@ -140,7 +141,8 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum, OffsetNumber minoff; OffsetNumber maxoff; BTReadPageState pstate; - bool arrayKeys; + bool arrayKeys, + ignore_killed_tuples = scan->ignore_killed_tuples; int itemIndex, indnatts; @@ -151,7 +153,7 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum, so->currPos.prevPage = opaque->btpo_prev; so->currPos.nextPage = opaque->btpo_next; /* delay setting so->currPos.lsn until _bt_drop_lock_and_maybe_pin */ - so->currPos.dir = dir; + pstate.dir = so->currPos.dir = dir; so->currPos.nextTupleOffset = 0; /* either moreRight or moreLeft should be set now (may be unset later) */ @@ -244,7 +246,7 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum, * If the scan specifies not to return killed tuples, then we * treat a killed tuple as not passing the qual */ - if (scan->ignore_killed_tuples && ItemIdIsDead(iid)) + if (ignore_killed_tuples && ItemIdIsDead(iid)) { offnum = OffsetNumberNext(offnum); continue; @@ -402,7 +404,7 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum, * uselessly advancing to the page to the left. This is similar * to the high key optimization used by forward scans. */ - if (scan->ignore_killed_tuples && ItemIdIsDead(iid)) + if (ignore_killed_tuples && ItemIdIsDead(iid)) { if (offnum > minoff) { @@ -1157,8 +1159,8 @@ _bt_checkkeys(IndexScanDesc scan, BTReadPageState *pstate, bool arrayKeys, IndexTuple tuple, int tupnatts) { TupleDesc tupdesc = RelationGetDescr(scan->indexRelation); - BTScanOpaque so = (BTScanOpaque) scan->opaque; - ScanDirection dir = so->currPos.dir; + BTScanOpaque so PG_USED_FOR_ASSERTS_ONLY = (BTScanOpaque) scan->opaque; + ScanDirection dir = pstate->dir; int ikey = pstate->startikey; bool res; @@ -2059,8 +2061,7 @@ static void _bt_checkkeys_look_ahead(IndexScanDesc scan, BTReadPageState *pstate, int tupnatts, TupleDesc tupdesc) { - BTScanOpaque so = (BTScanOpaque) scan->opaque; - ScanDirection dir = so->currPos.dir; + ScanDirection dir = pstate->dir; OffsetNumber aheadoffnum; IndexTuple ahead; @@ -2193,7 +2194,7 @@ _bt_advance_array_keys(IndexScanDesc scan, BTReadPageState *pstate, { BTScanOpaque so = (BTScanOpaque) scan->opaque; Relation rel = scan->indexRelation; - ScanDirection dir = so->currPos.dir; + ScanDirection dir = pstate ? pstate->dir : ForwardScanDirection; int arrayidx = 0; bool beyond_end_advance = false, skip_array_advanced = false, |