diff options
| -rw-r--r-- | src/backend/access/nbtree/nbtpreprocesskeys.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/src/backend/access/nbtree/nbtpreprocesskeys.c b/src/backend/access/nbtree/nbtpreprocesskeys.c index 8eb4bb8410e..21c519cd108 100644 --- a/src/backend/access/nbtree/nbtpreprocesskeys.c +++ b/src/backend/access/nbtree/nbtpreprocesskeys.c @@ -752,9 +752,12 @@ _bt_fix_scankey_strategy(ScanKey skey, int16 *indoption) * * Depending on the operator type, the key may be required for both scan * directions or just one. Also, if the key is a row comparison header, - * we have to mark its first subsidiary ScanKey as required. (Subsequent - * subsidiary ScanKeys are normally for lower-order columns, and thus - * cannot be required, since they're after the first non-equality scankey.) + * we have to mark the appropriate subsidiary ScanKeys as required. In such + * cases, the first subsidiary key is required, but subsequent ones are + * required only as long as they correspond to successive index columns and + * match the leading column as to sort direction. Otherwise the row + * comparison ordering is different from the index ordering and so we can't + * stop the scan on the basis of those lower-order columns. * * Note: when we set required-key flag bits in a subsidiary scankey, we are * scribbling on a data structure belonging to the index AM's caller, not on |