database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-03 20:02:46 +03:00
Code Activity

Revise the planner's handling of "pseudoconstant" WHERE clauses, that is

Browse Source 
clauses containing no variables and no volatile functions.  Such a clause
can be used as a one-time qual in a gating Result plan node, to suppress
plan execution entirely when it is false.  Even when the clause is true,
putting it in a gating node wins by avoiding repeated evaluation of the
clause.  In previous PG releases, query_planner() would do this for
pseudoconstant clauses appearing at the top level of the jointree, but
there was no ability to generate a gating Result deeper in the plan tree.
To fix it, get rid of the special case in query_planner(), and instead
process pseudoconstant clauses through the normal RestrictInfo qual
distribution mechanism.  When a pseudoconstant clause is found attached to
a path node in create_plan(), pull it out and generate a gating Result at
that point.  This requires special-casing pseudoconstants in selectivity
estimation and cost_qual_eval, but on the whole it's pretty clean.
It probably even makes the planner a bit faster than before for the normal
case of no pseudoconstants, since removing pull_constant_clauses saves one
useless traversal of the qual tree.  Per gripe from Phil Frost.
This commit is contained in:
Tom Lane
2006-07-01 18:38:33 +00:00
parent 68628fc38e
commit cffd89ca73
20 changed files with 464 additions and 294 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
src/backend/optimizer/path/indxpath.c
View File

@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.208 2006/06/07 17:08:07 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.209 2006/07/01 18:38:32 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -998,6 +998,15 @@ match_clause_to_indexcol(IndexOptInfo *index,
Oid expr_op;
bool plain_op;
/*
* Never match pseudoconstants to indexes. (Normally this could not
* happen anyway, since a pseudoconstant clause couldn't contain a
* Var, but what if someone builds an expression index on a constant?
* It's not totally unreasonable to do so with a partial index, either.)
*/
if (rinfo->pseudoconstant)
return false;
/* First check for boolean-index cases. */
if (IsBooleanOpclass(opclass))
{
@ -2212,6 +2221,7 @@ expand_indexqual_conditions(IndexOptInfo *index, List *clausegroups)
make_restrictinfo(boolqual,
true,
false,
false,
NULL));
continue;
}
@ -2577,7 +2587,7 @@ expand_indexqual_rowcompare(RestrictInfo *rinfo,
matching_cols);
rc->rargs = list_truncate((List *) copyObject(clause->rargs),
matching_cols);
return make_restrictinfo((Expr *) rc, true, false, NULL);
return make_restrictinfo((Expr *) rc, true, false, false, NULL);
}
else
{
@ -2586,7 +2596,7 @@ expand_indexqual_rowcompare(RestrictInfo *rinfo,
opexpr = make_opclause(linitial_oid(new_ops), BOOLOID, false,
copyObject(linitial(clause->largs)),
copyObject(linitial(clause->rargs)));
return make_restrictinfo(opexpr, true, false, NULL);
return make_restrictinfo(opexpr, true, false, false, NULL);
}
}
@ -2678,7 +2688,7 @@ prefix_quals(Node *leftop, Oid opclass,
elog(ERROR, "no = operator for opclass %u", opclass);
expr = make_opclause(oproid, BOOLOID, false,
(Expr *) leftop, (Expr *) prefix_const);
result = list_make1(make_restrictinfo(expr, true, false, NULL));
result = list_make1(make_restrictinfo(expr, true, false, false, NULL));
return result;
}
@ -2693,7 +2703,7 @@ prefix_quals(Node *leftop, Oid opclass,
elog(ERROR, "no >= operator for opclass %u", opclass);
expr = make_opclause(oproid, BOOLOID, false,
(Expr *) leftop, (Expr *) prefix_const);
result = list_make1(make_restrictinfo(expr, true, false, NULL));
result = list_make1(make_restrictinfo(expr, true, false, false, NULL));
/*-------
* If we can create a string larger than the prefix, we can say
@ -2709,7 +2719,8 @@ prefix_quals(Node *leftop, Oid opclass,
elog(ERROR, "no < operator for opclass %u", opclass);
expr = make_opclause(oproid, BOOLOID, false,
(Expr *) leftop, (Expr *) greaterstr);
result = lappend(result, make_restrictinfo(expr, true, false, NULL));
result = lappend(result,
make_restrictinfo(expr, true, false, false, NULL));
}
return result;
@ -2772,7 +2783,7 @@ network_prefix_quals(Node *leftop, Oid expr_op, Oid opclass, Datum rightop)
(Expr *) leftop,
(Expr *) makeConst(datatype, -1, opr1right,
false, false));
result = list_make1(make_restrictinfo(expr, true, false, NULL));
result = list_make1(make_restrictinfo(expr, true, false, false, NULL));
/* create clause "key <= network_scan_last( rightop )" */
@ -2787,7 +2798,8 @@ network_prefix_quals(Node *leftop, Oid expr_op, Oid opclass, Datum rightop)
(Expr *) leftop,
(Expr *) makeConst(datatype, -1, opr2right,
false, false));
result = lappend(result, make_restrictinfo(expr, true, false, NULL));
result = lappend(result,
make_restrictinfo(expr, true, false, false, NULL));
return result;
}