diff options
Diffstat (limited to 'src/backend/access/nbtree/nbtutils.c')
| -rw-r--r-- | src/backend/access/nbtree/nbtutils.c | 157 |
1 files changed, 86 insertions, 71 deletions
diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c index eb6dbfda33c..9aed207995f 100644 --- a/src/backend/access/nbtree/nbtutils.c +++ b/src/backend/access/nbtree/nbtutils.c @@ -2442,32 +2442,8 @@ _bt_set_startikey(IndexScanDesc scan, BTReadPageState *pstate) } if (key->sk_flags & SK_ROW_HEADER) { - /* - * RowCompare inequality. - * - * Only the first subkey from a RowCompare can ever be marked - * required (that happens when the row header is marked required). - * There is no simple, general way for us to transitively deduce - * whether or not every tuple on the page satisfies a RowCompare - * key based only on firsttup and lasttup -- so we just give up. - */ - if (!start_past_saop_eq && !so->skipScan) - break; /* unsafe to go further */ - - /* - * We have to be even more careful with RowCompares that come - * after an array: we assume it's unsafe to even bypass the array. - * Calling _bt_start_array_keys to recover the scan's arrays - * following use of forcenonrequired mode isn't compatible with - * _bt_check_rowcompare's continuescan=false behavior with NULL - * row compare members. _bt_advance_array_keys must not make a - * decision on the basis of a key not being satisfied in the - * opposite-to-scan direction until the scan reaches a leaf page - * where the same key begins to be satisfied in scan direction. - * The _bt_first !used_all_subkeys behavior makes this limitation - * hard to work around some other way. - */ - return; /* completely unsafe to set pstate.startikey */ + /* RowCompare inequalities currently aren't supported */ + break; /* "unsafe" */ } if (key->sk_strategy != BTEqualStrategyNumber) { @@ -2964,6 +2940,31 @@ _bt_check_rowcompare(ScanKey skey, IndexTuple tuple, int tupnatts, Assert(subkey->sk_flags & SK_ROW_MEMBER); + /* When a NULL row member is compared, the row never matches */ + if (subkey->sk_flags & SK_ISNULL) + { + /* + * Unlike the simple-scankey case, this isn't a disallowed case + * (except when it's the first row element that has the NULL arg). + * But it can never match. If all the earlier row comparison + * columns are required for the scan direction, we can stop the + * scan, because there can't be another tuple that will succeed. + */ + Assert(subkey != (ScanKey) DatumGetPointer(skey->sk_argument)); + subkey--; + if (forcenonrequired) + { + /* treating scan's keys as non-required */ + } + else if ((subkey->sk_flags & SK_BT_REQFWD) && + ScanDirectionIsForward(dir)) + *continuescan = false; + else if ((subkey->sk_flags & SK_BT_REQBKWD) && + ScanDirectionIsBackward(dir)) + *continuescan = false; + return false; + } + if (subkey->sk_attno > tupnatts) { /* @@ -2973,11 +2974,7 @@ _bt_check_rowcompare(ScanKey skey, IndexTuple tuple, int tupnatts, * attribute passes the qual. */ Assert(BTreeTupleIsPivot(tuple)); - cmpresult = 0; - if (subkey->sk_flags & SK_ROW_END) - break; - subkey++; - continue; + return true; } datum = index_getattr(tuple, @@ -2987,6 +2984,8 @@ _bt_check_rowcompare(ScanKey skey, IndexTuple tuple, int tupnatts, if (isNull) { + int reqflags; + if (forcenonrequired) { /* treating scan's keys as non-required */ @@ -2997,15 +2996,35 @@ _bt_check_rowcompare(ScanKey skey, IndexTuple tuple, int tupnatts, * Since NULLs are sorted before non-NULLs, we know we have * reached the lower limit of the range of values for this * index attr. On a backward scan, we can stop if this qual - * is one of the "must match" subset. We can stop regardless - * of whether the qual is > or <, so long as it's required, - * because it's not possible for any future tuples to pass. On - * a forward scan, however, we must keep going, because we may - * have initially positioned to the start of the index. - * (_bt_advance_array_keys also relies on this behavior during - * forward scans.) + * is one of the "must match" subset. However, on a forwards + * scan, we must keep going, because we may have initially + * positioned to the start of the index. + * + * All required NULLS FIRST > row members can use NULL tuple + * values to end backwards scans, just like with other values. + * A qual "WHERE (a, b, c) > (9, 42, 'foo')" can terminate a + * backwards scan upon reaching the index's rightmost "a = 9" + * tuple whose "b" column contains a NULL (if not sooner). + * Since "b" is NULLS FIRST, we can treat its NULLs as "<" 42. + */ + reqflags = SK_BT_REQBKWD; + + /* + * When a most significant required NULLS FIRST < row compare + * member sees NULL tuple values during a backwards scan, it + * signals the end of matches for the whole row compare/scan. + * A qual "WHERE (a, b, c) < (9, 42, 'foo')" will terminate a + * backwards scan upon reaching the rightmost tuple whose "a" + * column has a NULL. The "a" NULL value is "<" 9, and yet + * our < row compare will still end the scan. (This isn't + * safe with later/lower-order row members. Notice that it + * can only happen with an "a" NULL some time after the scan + * completely stops needing to use its "b" and "c" members.) */ - if ((subkey->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD)) && + if (subkey == (ScanKey) DatumGetPointer(skey->sk_argument)) + reqflags |= SK_BT_REQFWD; /* safe, first row member */ + + if ((subkey->sk_flags & reqflags) && ScanDirectionIsBackward(dir)) *continuescan = false; } @@ -3015,15 +3034,35 @@ _bt_check_rowcompare(ScanKey skey, IndexTuple tuple, int tupnatts, * Since NULLs are sorted after non-NULLs, we know we have * reached the upper limit of the range of values for this * index attr. On a forward scan, we can stop if this qual is - * one of the "must match" subset. We can stop regardless of - * whether the qual is > or <, so long as it's required, - * because it's not possible for any future tuples to pass. On - * a backward scan, however, we must keep going, because we - * may have initially positioned to the end of the index. - * (_bt_advance_array_keys also relies on this behavior during - * backward scans.) + * one of the "must match" subset. However, on a backward + * scan, we must keep going, because we may have initially + * positioned to the end of the index. + * + * All required NULLS LAST < row members can use NULL tuple + * values to end forwards scans, just like with other values. + * A qual "WHERE (a, b, c) < (9, 42, 'foo')" can terminate a + * forwards scan upon reaching the index's leftmost "a = 9" + * tuple whose "b" column contains a NULL (if not sooner). + * Since "b" is NULLS LAST, we can treat its NULLs as ">" 42. + */ + reqflags = SK_BT_REQFWD; + + /* + * When a most significant required NULLS LAST > row compare + * member sees NULL tuple values during a forwards scan, it + * signals the end of matches for the whole row compare/scan. + * A qual "WHERE (a, b, c) > (9, 42, 'foo')" will terminate a + * forwards scan upon reaching the leftmost tuple whose "a" + * column has a NULL. The "a" NULL value is ">" 9, and yet + * our > row compare will end the scan. (This isn't safe with + * later/lower-order row members. Notice that it can only + * happen with an "a" NULL some time after the scan completely + * stops needing to use its "b" and "c" members.) */ - if ((subkey->sk_flags & (SK_BT_REQFWD | SK_BT_REQBKWD)) && + if (subkey == (ScanKey) DatumGetPointer(skey->sk_argument)) + reqflags |= SK_BT_REQBKWD; /* safe, first row member */ + + if ((subkey->sk_flags & reqflags) && ScanDirectionIsForward(dir)) *continuescan = false; } @@ -3034,30 +3073,6 @@ _bt_check_rowcompare(ScanKey skey, IndexTuple tuple, int tupnatts, return false; } - if (subkey->sk_flags & SK_ISNULL) - { - /* - * Unlike the simple-scankey case, this isn't a disallowed case - * (except when it's the first row element that has the NULL arg). - * But it can never match. If all the earlier row comparison - * columns are required for the scan direction, we can stop the - * scan, because there can't be another tuple that will succeed. - */ - Assert(subkey != (ScanKey) DatumGetPointer(skey->sk_argument)); - subkey--; - if (forcenonrequired) - { - /* treating scan's keys as non-required */ - } - else if ((subkey->sk_flags & SK_BT_REQFWD) && - ScanDirectionIsForward(dir)) - *continuescan = false; - else if ((subkey->sk_flags & SK_BT_REQBKWD) && - ScanDirectionIsBackward(dir)) - *continuescan = false; - return false; - } - /* Perform the test --- three-way comparison not bool operator */ cmpresult = DatumGetInt32(FunctionCall2Coll(&subkey->sk_func, subkey->sk_collation, |