diff options
Diffstat (limited to 'src/backend/access/nbtree/nbtsearch.c')
| -rw-r--r-- | src/backend/access/nbtree/nbtsearch.c | 42 |
1 files changed, 24 insertions, 18 deletions
diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c index b0c65a42d6d..82122464d5d 100644 --- a/src/backend/access/nbtree/nbtsearch.c +++ b/src/backend/access/nbtree/nbtsearch.c @@ -1530,7 +1530,8 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum, int itemIndex; bool continuescan; int indnatts; - bool requiredMatchedByPrecheck; + bool continuescanPrechecked; + bool haveFirstMatch = false; /* * We must have the buffer pinned and locked, but the usual macro can't be @@ -1585,12 +1586,11 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum, Assert(BTScanPosIsPinned(so->currPos)); /* - * Prechecking the page with scan keys required for direction scan. We - * check these keys with the last item on the page (according to our scan - * direction). If these keys are matched, we can skip checking them with - * every item on the page. Scan keys for our scan direction would - * necessarily match the previous items. Scan keys required for opposite - * direction scan are already matched by the _bt_first() call. + * Prechecking the value of the continuescan flag for the last item on the + * page (for backwards scan it will be the first item on a page). If we + * observe it to be true, then it should be true for all other items. This + * allows us to do significant optimizations in the _bt_checkkeys() + * function for all the items on the page. * * With the forward scan, we do this check for the last item on the page * instead of the high key. It's relatively likely that the most @@ -1610,17 +1610,17 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum, itup = (IndexTuple) PageGetItem(page, iid); /* - * Do the precheck. Note that we pass the pointer to - * 'requiredMatchedByPrecheck' to 'continuescan' argument. That will + * Do the precheck. Note that we pass the pointer to the + * 'continuescanPrechecked' to the 'continuescan' argument. That will * set flag to true if all required keys are satisfied and false * otherwise. */ (void) _bt_checkkeys(scan, itup, indnatts, dir, - &requiredMatchedByPrecheck, false); + &continuescanPrechecked, false, false); } else { - requiredMatchedByPrecheck = false; + continuescanPrechecked = false; } if (ScanDirectionIsForward(dir)) @@ -1650,19 +1650,22 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum, Assert(!BTreeTupleIsPivot(itup)); passes_quals = _bt_checkkeys(scan, itup, indnatts, dir, - &continuescan, requiredMatchedByPrecheck); + &continuescan, + continuescanPrechecked, + haveFirstMatch); /* * If the result of prechecking required keys was true, then in * assert-enabled builds we also recheck that the _bt_checkkeys() * result is the same. */ - Assert(!requiredMatchedByPrecheck || + Assert((!continuescanPrechecked && haveFirstMatch) || passes_quals == _bt_checkkeys(scan, itup, indnatts, dir, - &continuescan, false)); + &continuescan, false, false)); if (passes_quals) { /* tuple passes all scan key conditions */ + haveFirstMatch = true; if (!BTreeTupleIsPosting(itup)) { /* Remember it */ @@ -1717,7 +1720,7 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum, int truncatt; truncatt = BTreeTupleGetNAtts(itup, scan->indexRelation); - _bt_checkkeys(scan, itup, truncatt, dir, &continuescan, false); + _bt_checkkeys(scan, itup, truncatt, dir, &continuescan, false, false); } if (!continuescan) @@ -1770,19 +1773,22 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum, Assert(!BTreeTupleIsPivot(itup)); passes_quals = _bt_checkkeys(scan, itup, indnatts, dir, - &continuescan, requiredMatchedByPrecheck); + &continuescan, + continuescanPrechecked, + haveFirstMatch); /* * If the result of prechecking required keys was true, then in * assert-enabled builds we also recheck that the _bt_checkkeys() * result is the same. */ - Assert(!requiredMatchedByPrecheck || + Assert((!continuescanPrechecked && !haveFirstMatch) || passes_quals == _bt_checkkeys(scan, itup, indnatts, dir, - &continuescan, false)); + &continuescan, false, false)); if (passes_quals && tuple_alive) { /* tuple passes all scan key conditions */ + haveFirstMatch = true; if (!BTreeTupleIsPosting(itup)) { /* Remember it */ |