Commit336879f

committed

Improve find_em_expr_usable_for_sorting_rel comment

Clarify the relationship between find_em_expr_usable_for_sorting_rel andprepare_sort_from_pathkeys, i.e. what restrictions need to be sharedbetween those two places.Author: James ColemanReviewed-by: Tomas VondraBackpatch-through: 13Discussion:https://postgr.es/m/CAAaqYe8cK3g5CfLC4w7bs%3DhC0mSksZC%3DH5M8LSchj5e5OxpTAg%40mail.gmail.com

1 parentaa97890 commit336879fCopy full SHA for 336879f

File tree

-3

lines changed

-3

lines changed

Lines changed: 5 additions & 3 deletions

Original file line number	Diff line number	Diff line change
`@@ -795,9 +795,11 @@ find_em_expr_for_rel(EquivalenceClass ec, RelOptInfo rel)`
`795`	`795`	`}`
`796`	`796`
`797`	`797`	`/*`
`798`		`- * Find an equivalence class member expression that can be safely used by a`
`799`		`- * sort node on top of the provided relation. The rules here must match those`
`800`		`- * applied in prepare_sort_from_pathkeys.`
	`798`	`+ * Find an equivalence class member expression that can be safely used to build`
	`799`	`+ * a sort node using the provided relation. The rules are a subset of those`
	`800`	`+ * applied in prepare_sort_from_pathkeys since that function deals with sorts`
	`801`	`+ * that must be delayed until the last stages of query execution, while here`
	`802`	`+ * we only care about proactive sorts.`
`801`	`803`	`*/`
`802`	`804`	`Expr*`
`803`	`805`	`find_em_expr_usable_for_sorting_rel(PlannerInforoot,EquivalenceClassec,`

Lines changed: 3 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -5844,6 +5844,9 @@ make_incrementalsort(Plan *lefttree, int numCols, int nPresortedCols,`
`5844`	`5844`	`*`
`5845`	`5845`	`* Returns the node which is to be the input to the Sort (either lefttree,`
`5846`	`5846`	`* or a Result stacked atop lefttree).`
	`5847`	`+ *`
	`5848`	`+ * Note: Restrictions on what expressions are safely sortable may also need to`
	`5849`	`+ * be added to find_em_expr_usable_for_sorting_rel.`
`5847`	`5850`	`*/`
`5848`	`5851`	`staticPlan*`
`5849`	`5852`	`prepare_sort_from_pathkeys(Planlefttree,Listpathkeys,`

Comments

(0)