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Simple constraint exclusion. For now, only child tables of inheritance

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scans are candidates for exclusion; this should be fixed eventually.
Simon Riggs, with some help from Tom Lane.
This commit is contained in:
Tom Lane
2005-07-23 21:05:48 +00:00
parent 9af9d674c6
commit d007a95055
14 changed files with 621 additions and 105 deletions
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20
src/include/nodes/relation.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.116 2005/07/02 23:00:42 tgl Exp $
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.117 2005/07/23 21:05:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -516,6 +516,9 @@ typedef struct TidPath
* AppendPath represents an Append plan, ie, successive execution of
* several member plans. Currently it is only used to handle expansion
* of inheritance trees.
*
* Note: it is possible for "subpaths" to contain only one, or even no,
* elements. These cases are optimized during create_append_plan.
*/
typedef struct AppendPath
{
@@ -524,10 +527,17 @@ typedef struct AppendPath
} AppendPath;
/*
* ResultPath represents use of a Result plan node, either to compute a
* variable-free targetlist or to gate execution of a subplan with a
* one-time (variable-free) qual condition. Note that in the former case
* path.parent will be NULL; in the latter case it is copied from the subpath.
* ResultPath represents use of a Result plan node. There are several
* applications for this:
* * To compute a variable-free targetlist (a "SELECT expressions" query).
* In this case subpath and path.parent will both be NULL. constantqual
* might or might not be empty ("SELECT expressions WHERE something").
* * To gate execution of a subplan with a one-time (variable-free) qual
* condition. path.parent is copied from the subpath.
* * To substitute for a scan plan when we have proven that no rows in
* a table will satisfy the query. subpath is NULL but path.parent
* references the not-to-be-scanned relation, and constantqual is
* a constant FALSE.
*
* Note that constantqual is a list of bare clauses, not RestrictInfos.
*/