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pathkeys fixes

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This commit is contained in:
Bruce Momjian
1999-02-20 19:02:43 +00:00
parent 0ff2733355
commit 75cccd0ad3
4 changed files with 55 additions and 24 deletions
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48
src/backend/optimizer/path/pathkeys.c
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@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.4 1999/02/20 18:01:01 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.5 1999/02/20 19:02:41 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -54,7 +54,19 @@ static List *new_matching_subkeys(Var *subkey, List *considered_subkeys,
* { {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
* is a List of Lists. -- bjm
* is a List of Lists.
*
* For multi-key sorts, if the outer is sorted by a multi-key index, the
* multi-key index remains after the join. If the inner has a multi-key
* sort, only the primary key of the inner is added to the result.
* Mergejoins only join on the primary key. Currently, non-primary keys
* in the pathkeys List are of limited value.
*
* HashJoin has similar functionality. NestJoin does not perform sorting,
* and allows non-equajoins, so it does not allow useful pathkeys.
*
* -- bjm
*
*/
/****************************************************************************
@ -92,10 +104,10 @@ static List *new_matching_subkeys(Var *subkey, List *considered_subkeys,
*/
List *
order_joinkeys_by_pathkeys(List *pathkeys,
List *joinkeys,
List *joinclauses,
int outer_or_inner,
List **matchedJoinClausesPtr)
List *joinkeys,
List *joinclauses,
int outer_or_inner,
List **matchedJoinClausesPtr)
{
List *matched_joinkeys = NIL;
List *matched_joinclauses = NIL;
@ -103,6 +115,10 @@ order_joinkeys_by_pathkeys(List *pathkeys,
List *i = NIL;
int matched_joinkey_index = -1;
/*
* Reorder the joinkeys by picking out one that matches each pathkey,
* and create a new joinkey/joinclause list in pathkey order
*/
foreach(i, pathkeys)
{
pathkey = lfirst(i);
@ -118,10 +134,18 @@ order_joinkeys_by_pathkeys(List *pathkeys,
matched_joinclauses = lappend(matched_joinclauses, joinclause);
}
else
{
/* A pathkey could not be matched. */
break;
}
/*
* Did we fail to match all the joinkeys?
* Extra pathkeys are no problem.
*/
if (length(joinkeys) != length(matched_joinkeys))
{
*matchedJoinClausesPtr = NIL;
return NIL;
}
}
*matchedJoinClausesPtr = matched_joinclauses;
@ -133,6 +157,8 @@ order_joinkeys_by_pathkeys(List *pathkeys,
* match_pathkey_joinkeys
* Returns the 0-based index into 'joinkeys' of the first joinkey whose
* outer or inner subkey matches any subkey of 'pathkey'.
*
* All these keys are equivalent, so any of them can match. See above.
*/
static int
match_pathkey_joinkeys(List *pathkey,
@ -141,8 +167,7 @@ match_pathkey_joinkeys(List *pathkey,
{
Var *path_subkey;
int pos;
List *i = NIL;
List *x = NIL;
List *i, *x;
JoinKey *jk;
foreach(i, pathkey)
@ -152,8 +177,7 @@ match_pathkey_joinkeys(List *pathkey,
foreach(x, joinkeys)
{
jk = (JoinKey *) lfirst(x);
if (var_equal(path_subkey,
extract_join_key(jk, outer_or_inner)))
if (var_equal(path_subkey, extract_join_key(jk, outer_or_inner)))
return pos;
pos++;
}