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Add a reverse-translation column number array to struct AppendRelInfo.

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This provides for cheaper mapping of child columns back to parent
columns.  The one existing use-case in examine_simple_variable()
would hardly justify this by itself; but an upcoming bug fix will
make use of this array in a mainstream code path, and it seems
likely that we'll find other uses for it as we continue to build
out the partitioning infrastructure.

Discussion: https://postgr.es/m/12424.1575168015@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2019-12-02 18:05:29 -05:00
parent 4526951d56
commit ce76c0ba53
8 changed files with 61 additions and 39 deletions
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18
src/backend/optimizer/prep/prepjointree.c
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@@ -81,7 +81,7 @@ static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root,
int parentRTindex, Query *setOpQuery,
int childRToffset);
static void make_setop_translation_list(Query *query, Index newvarno,
List **translated_vars);
AppendRelInfo *appinfo);
static bool is_simple_subquery(Query *subquery, RangeTblEntry *rte,
JoinExpr *lowest_outer_join);
static Node *pull_up_simple_values(PlannerInfo *root, Node *jtnode,
@@ -1313,8 +1313,7 @@ pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex,
appinfo->child_relid = childRTindex;
appinfo->parent_reltype = InvalidOid;
appinfo->child_reltype = InvalidOid;
make_setop_translation_list(setOpQuery, childRTindex,
&appinfo->translated_vars);
make_setop_translation_list(setOpQuery, childRTindex, appinfo);
appinfo->parent_reloid = InvalidOid;
root->append_rel_list = lappend(root->append_rel_list, appinfo);
@@ -1356,14 +1355,22 @@ pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex,
* a UNION ALL member. (At this point it's just a simple list of
* referencing Vars, but if we succeed in pulling up the member
* subquery, the Vars will get replaced by pulled-up expressions.)
* Also create the rather trivial reverse-translation array.
*/
static void
make_setop_translation_list(Query *query, Index newvarno,
List **translated_vars)
AppendRelInfo *appinfo)
{
List *vars = NIL;
AttrNumber *pcolnos;
ListCell *l;
/* Initialize reverse-translation array with all entries zero */
/* (entries for resjunk columns will stay that way) */
appinfo->num_child_cols = list_length(query->targetList);
appinfo->parent_colnos = pcolnos =
(AttrNumber *) palloc0(appinfo->num_child_cols * sizeof(AttrNumber));
foreach(l, query->targetList)
{
TargetEntry *tle = (TargetEntry *) lfirst(l);
@@ -1372,9 +1379,10 @@ make_setop_translation_list(Query *query, Index newvarno,
continue;
vars = lappend(vars, makeVarFromTargetEntry(newvarno, tle));
pcolnos[tle->resno - 1] = tle->resno;
}
*translated_vars = vars;
appinfo->translated_vars = vars;
}
/*