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| author | Bruce Momjian <bruce@momjian.us> | 1999-02-20 16:32:35 +0000 |
|---|---|---|
| committer | Bruce Momjian <bruce@momjian.us> | 1999-02-20 16:32:35 +0000 |
| commit | 148ec3b1d888f18cd5579c0e31dbc615a941a993 (patch) | |
| tree | 80003a61600b5000d8cdf25146fc7975757217b0 /src | |
| parent | 9188aab758b94cc72bdf99a03ae2bbefa95e61f7 (diff) | |
| download | postgresql-148ec3b1d888f18cd5579c0e31dbc615a941a993.tar.gz postgresql-148ec3b1d888f18cd5579c0e31dbc615a941a993.zip | |
update pathkey description.
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/path/pathkeys.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c index 29f11dcd1c4..e19eeec01ff 100644 --- a/src/backend/optimizer/path/pathkeys.c +++ b/src/backend/optimizer/path/pathkeys.c @@ -7,7 +7,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.2 1999/02/20 16:28:20 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.3 1999/02/20 16:32:35 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -38,7 +38,7 @@ static List *new_matching_subkeys(Var *subkey, List *considered_subkeys, /* * Explanation of Path.pathkeys * - * This structure is a List of List of Var nodes that represent the sort + * Path.pathkeys is a List of List of Var nodes that represent the sort * order of the result generated by the Path. * * In single/base relation RelOptInfo's, the Path's represent various ways @@ -49,8 +49,8 @@ static List *new_matching_subkeys(Var *subkey, List *considered_subkeys, * * Multi-relation RelOptInfo Path's are more complicated. Mergejoins are * only performed with equajoins("="). Because of this, the multi-relation - * path actually has more than one ordering. For example, a mergejoin Path - * of "tab1.col1 = tab2.col1" would generate a pathkeys of + * path actually has more than one primary Var key. For example, a + * mergejoin Path of "tab1.col1 = tab2.col1" would generate a pathkeys of * { {tab1.col1, tab2.col1} }. This allows future joins to use either Var * as a pre-sorted key to prevent Mergejoins from having to re-sort the Path. * They are equal, so they are both primary sort keys. This is why pathkeys |