diff options
Diffstat (limited to 'src/backend/optimizer/util/keys.c')
| -rw-r--r-- | src/backend/optimizer/util/keys.c | 76 |
1 files changed, 42 insertions, 34 deletions
diff --git a/src/backend/optimizer/util/keys.c b/src/backend/optimizer/util/keys.c index 123b6dc4cb4..c921c24c0d1 100644 --- a/src/backend/optimizer/util/keys.c +++ b/src/backend/optimizer/util/keys.c @@ -7,7 +7,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/util/Attic/keys.c,v 1.18 1999/02/19 02:05:16 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/util/Attic/keys.c,v 1.19 1999/02/20 18:01:02 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -110,62 +110,70 @@ extract_join_key(JoinKey *jk, int outer_or_inner) * Returns t iff two sets of path keys are equivalent. They are * equivalent if the first Var nodes match the second Var nodes. * - * XXX It isn't necessary to check that each sublist exactly contain - * the same elements because if the routine that built these - * sublists together is correct, having one element in common - * implies having all elements in common. - * Huh? bjm + * See the top of optimizer/path/pathkeys.c for a description of pathkeys. + * Each pathkey is ordered by its join order, so they not pre-ordered to + * match. We must search them ourselves. * + * This gets called a lot, so it is optimized. */ bool pathkeys_match(List *keys1, List *keys2, int *better_key) { List *key1, - *key2, - *key1a, - *key2a; + *key2; + bool key1_subsetof_key2 = true, + key2_subsetof_key1 = true; for (key1 = keys1, key2 = keys2; key1 != NIL && key2 != NIL; key1 = lnext(key1), key2 = lnext(key2)) { - for (key1a = lfirst(key1), key2a = lfirst(key2); - key1a != NIL && key2a != NIL; - key1a = lnext(key1a), key2a = lnext(key2a)) - if (!equal(lfirst(key1a), lfirst(key2a))) + List *i; + + if (key1_subsetof_key2) + foreach(i, lfirst(key1)) { - *better_key = 0; - return false; + Var *subkey = lfirst(i); + if (!member(subkey, lfirst(key2))) + { + key1_subsetof_key2 = false; + break; + } } - if (key1a != NIL && key2a == NIL) - { - *better_key = 1; - return true; - } - if (key1a == NIL && key2a != NIL) - { - *better_key = 2; - return true; - } + + if (key2_subsetof_key1) + foreach(i, lfirst(key2)) + { + Var *subkey = lfirst(i); + if (!member(subkey, lfirst(key1))) + { + key2_subsetof_key1 = false; + break; + } + } + if (!key1_subsetof_key2 && !key2_subsetof_key1) + break; /* no need to continue comparisons. */ } - /* Now the result should be true if list keys2 has at least as many - * entries as keys1, ie, we did not fall off the end of keys2 first. - * If key1 is now NIL then we hit the end of keys1 before or at the - * same time as the end of keys2. - */ - if (key1 != NIL && key2 == NIL) + if (!key1_subsetof_key2 && !key2_subsetof_key1) { - *better_key = 1; - return true; + *better_key = 0; + return false; } - if (key1 == NIL && key2 != NIL) + if (key1_subsetof_key2 && !key2_subsetof_key1) { *better_key = 2; return true; } + if (!key1_subsetof_key2 && key2_subsetof_key1) + { + *better_key = 1; + return true; + } + *better_key = 0; return true; + } /* |