diff options
Diffstat (limited to 'src/include/nodes/relation.h')
| -rw-r--r-- | src/include/nodes/relation.h | 25 |
1 files changed, 18 insertions, 7 deletions
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h index 91f4c5c1c4..6e3d0f3518 100644 --- a/src/include/nodes/relation.h +++ b/src/include/nodes/relation.h @@ -256,9 +256,9 @@ typedef struct PlannerInfo * the entire append relation. The member RTEs are otherrels. The parent * is present in the query join tree but the members are not. The member * RTEs and otherrels are used to plan the scans of the individual tables or - * subqueries of the append set; then the parent baserel is given an Append - * plan comprising the best plans for the individual member rels. (See - * comments for AppendRelInfo for more information.) + * subqueries of the append set; then the parent baserel is given Append + * and/or MergeAppend paths comprising the best paths for the individual + * member rels. (See comments for AppendRelInfo for more information.) * * At one time we also made otherrels to represent join RTEs, for use in * handling join alias Vars. Currently this is not needed because all join @@ -542,10 +542,11 @@ typedef struct EquivalenceClass * * em_is_child signifies that this element was built by transposing a member * for an inheritance parent relation to represent the corresponding expression - * on an inheritance child. The element should be ignored for all purposes - * except constructing inner-indexscan paths for the child relation. (Other - * types of join are driven from transposed joininfo-list entries.) Note - * that the EC's ec_relids field does NOT include the child relation. + * on an inheritance child. These elements are used for constructing + * inner-indexscan paths for the child relation (other types of join are + * driven from transposed joininfo-list entries) and for constructing + * MergeAppend paths for the whole inheritance tree. Note that the EC's + * ec_relids field does NOT include the child relation. * * em_datatype is usually the same as exprType(em_expr), but can be * different when dealing with a binary-compatible opfamily; in particular @@ -756,6 +757,16 @@ typedef struct AppendPath (IsA((p), AppendPath) && ((AppendPath *) (p))->subpaths == NIL) /* + * MergeAppendPath represents a MergeAppend plan, ie, the merging of sorted + * results from several member plans to produce similarly-sorted output. + */ +typedef struct MergeAppendPath +{ + Path path; + List *subpaths; /* list of component Paths */ +} MergeAppendPath; + +/* * ResultPath represents use of a Result plan node to compute a variable-free * targetlist with no underlying tables (a "SELECT expressions" query). * The query could have a WHERE clause, too, represented by "quals". |