diff options
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 16 | ||||
| -rw-r--r-- | src/backend/utils/adt/selfuncs.c | 36 |
2 files changed, 41 insertions, 11 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 5146517132f..d0df5cab113 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -42,7 +42,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.101 2003/01/20 18:54:49 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.102 2003/01/22 20:16:40 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -791,8 +791,22 @@ cost_mergejoin(Path *path, Query *root, innerscansel = firstclause->left_mergescansel; } + /* convert selectivity to row count; must scan at least one row */ + outer_rows = ceil(outer_path->parent->rows * outerscansel); + if (outer_rows < 1) + outer_rows = 1; inner_rows = ceil(inner_path->parent->rows * innerscansel); + if (inner_rows < 1) + inner_rows = 1; + + /* + * Readjust scan selectivities to account for above rounding. This is + * normally an insignificant effect, but when there are only a few rows + * in the inputs, failing to do this makes for a large percentage error. + */ + outerscansel = outer_rows / outer_path->parent->rows; + innerscansel = inner_rows / inner_path->parent->rows; /* cost of source data */ diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index 42ad9f5f94b..20d353a0a50 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -15,7 +15,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.127 2003/01/20 18:54:59 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.128 2003/01/22 20:16:42 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -1742,7 +1742,9 @@ mergejoinscansel(Query *root, Node *clause, rsortop, ltop, gtop, - revltop; + leop, + revgtop, + revleop; Datum leftmax, rightmax; double selec; @@ -1780,35 +1782,49 @@ mergejoinscansel(Query *root, Node *clause, /* Look up the "left < right" and "left > right" operators */ op_mergejoin_crossops(opno, <op, >op, NULL, NULL); - /* Look up the "right < left" operator */ - revltop = get_commutator(gtop); - if (!OidIsValid(revltop)) - return; /* shouldn't happen */ + /* Look up the "left <= right" operator */ + leop = get_negator(gtop); + if (!OidIsValid(leop)) + return; /* insufficient info in catalogs */ + + /* Look up the "right > left" operator */ + revgtop = get_commutator(ltop); + if (!OidIsValid(revgtop)) + return; /* insufficient info in catalogs */ + + /* Look up the "right <= left" operator */ + revleop = get_negator(revgtop); + if (!OidIsValid(revleop)) + return; /* insufficient info in catalogs */ /* * Now, the fraction of the left variable that will be scanned is the * fraction that's <= the right-side maximum value. But only believe * non-default estimates, else stick with our 1.0. */ - selec = scalarineqsel(root, ltop, false, left, + selec = scalarineqsel(root, leop, false, left, rightmax, right->vartype); if (selec != DEFAULT_INEQ_SEL) *leftscan = selec; /* And similarly for the right variable. */ - selec = scalarineqsel(root, revltop, false, right, + selec = scalarineqsel(root, revleop, false, right, leftmax, left->vartype); if (selec != DEFAULT_INEQ_SEL) *rightscan = selec; /* * Only one of the two fractions can really be less than 1.0; believe - * the smaller estimate and reset the other one to exactly 1.0. + * the smaller estimate and reset the other one to exactly 1.0. If we + * get exactly equal estimates (as can easily happen with self-joins), + * believe neither. */ if (*leftscan > *rightscan) *leftscan = 1.0; - else + else if (*leftscan < *rightscan) *rightscan = 1.0; + else + *leftscan = *rightscan = 1.0; } /* |