diff options
Diffstat (limited to 'src/backend/optimizer/util/tlist.c')
| -rw-r--r-- | src/backend/optimizer/util/tlist.c | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/src/backend/optimizer/util/tlist.c b/src/backend/optimizer/util/tlist.c index cbc8c2b9fef..9f85dee3872 100644 --- a/src/backend/optimizer/util/tlist.c +++ b/src/backend/optimizer/util/tlist.c @@ -624,6 +624,17 @@ copy_pathtarget(PathTarget *src) } /* + * create_empty_pathtarget + * Create an empty (zero columns, zero cost) PathTarget. + */ +PathTarget * +create_empty_pathtarget(void) +{ + /* This is easy, but we don't want callers to hard-wire this ... */ + return (PathTarget *) palloc0(sizeof(PathTarget)); +} + +/* * add_column_to_pathtarget * Append a target column to the PathTarget. * @@ -656,6 +667,41 @@ add_column_to_pathtarget(PathTarget *target, Expr *expr, Index sortgroupref) } /* + * add_new_column_to_pathtarget + * Append a target column to the PathTarget, but only if it's not + * equal() to any pre-existing target expression. + * + * The caller cannot specify a sortgroupref, since it would be unclear how + * to merge that with a pre-existing column. + * + * As with make_pathtarget_from_tlist, we leave it to the caller to update + * the cost and width fields. + */ +void +add_new_column_to_pathtarget(PathTarget *target, Expr *expr) +{ + if (!list_member(target->exprs, expr)) + add_column_to_pathtarget(target, expr, 0); +} + +/* + * add_new_columns_to_pathtarget + * Apply add_new_column_to_pathtarget() for each element of the list. + */ +void +add_new_columns_to_pathtarget(PathTarget *target, List *exprs) +{ + ListCell *lc; + + foreach(lc, exprs) + { + Expr *expr = (Expr *) lfirst(lc); + + add_new_column_to_pathtarget(target, expr); + } +} + +/* * apply_pathtarget_labeling_to_tlist * Apply any sortgrouprefs in the PathTarget to matching tlist entries * |