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Re-implement LIMIT/OFFSET as a plan node type, instead of a hack in

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ExecutorRun.  This allows LIMIT to work in a view.  Also, LIMIT in a
cursor declaration will behave in a reasonable fashion, whereas before
it was overridden by the FETCH count.
This commit is contained in:
Tom Lane
2000-10-26 21:38:24 +00:00
parent c9476bafdb
commit 2f35b4efdb
26 changed files with 572 additions and 232 deletions
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28
src/backend/optimizer/plan/planner.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.92 2000/10/05 19:11:29 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.93 2000/10/26 21:36:09 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -341,8 +341,6 @@ is_simple_subquery(Query *subquery)
*/
if (subquery->rowMarks)
elog(ERROR, "FOR UPDATE is not supported in subselects");
if (subquery->limitOffset || subquery->limitCount)
elog(ERROR, "LIMIT is not supported in subselects");
/*
* Can't currently pull up a query with setops.
* Maybe after querytree redesign...
@ -350,13 +348,16 @@ is_simple_subquery(Query *subquery)
if (subquery->setOperations)
return false;
/*
* Can't pull up a subquery involving grouping, aggregation, or sorting.
* Can't pull up a subquery involving grouping, aggregation, sorting,
* or limiting.
*/
if (subquery->hasAggs ||
subquery->groupClause ||
subquery->havingQual ||
subquery->sortClause ||
subquery->distinctClause)
subquery->distinctClause ||
subquery->limitOffset ||
subquery->limitCount)
return false;
/*
* Hack: don't try to pull up a subquery with an empty jointree.
@ -831,7 +832,7 @@ union_planner(Query *parse,
}
else
{
/* It's a PARAM ... punt ... */
/* It's an expression ... punt ... */
tuple_fraction = 0.10;
}
}
@ -839,9 +840,8 @@ union_planner(Query *parse,
}
else
{
/*
* COUNT is a PARAM ... don't know exactly what the
* COUNT is an expression ... don't know exactly what the
* limit will be, but for lack of a better idea assume
* 10% of the plan's result is wanted.
*/
@ -1024,7 +1024,7 @@ union_planner(Query *parse,
}
/*
* Finally, if there is a DISTINCT clause, add the UNIQUE node.
* If there is a DISTINCT clause, add the UNIQUE node.
*/
if (parse->distinctClause)
{
@ -1032,6 +1032,16 @@ union_planner(Query *parse,
parse->distinctClause);
}
/*
* Finally, if there is a LIMIT/OFFSET clause, add the LIMIT node.
*/
if (parse->limitOffset || parse->limitCount)
{
result_plan = (Plan *) make_limit(tlist, result_plan,
parse->limitOffset,
parse->limitCount);
}
return result_plan;
}