From 7103ebb7aae8ab8076b7e85f335ceb8fe799097c Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Mon, 28 Mar 2022 16:45:58 +0200 Subject: Add support for MERGE SQL command MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit MERGE performs actions that modify rows in the target table using a source table or query. MERGE provides a single SQL statement that can conditionally INSERT/UPDATE/DELETE rows -- a task that would otherwise require multiple PL statements. For example, MERGE INTO target AS t USING source AS s ON t.tid = s.sid WHEN MATCHED AND t.balance > s.delta THEN UPDATE SET balance = t.balance - s.delta WHEN MATCHED THEN DELETE WHEN NOT MATCHED AND s.delta > 0 THEN INSERT VALUES (s.sid, s.delta) WHEN NOT MATCHED THEN DO NOTHING; MERGE works with regular tables, partitioned tables and inheritance hierarchies, including column and row security enforcement, as well as support for row and statement triggers and transition tables therein. MERGE is optimized for OLTP and is parameterizable, though also useful for large scale ETL/ELT. MERGE is not intended to be used in preference to existing single SQL commands for INSERT, UPDATE or DELETE since there is some overhead. MERGE can be used from PL/pgSQL. MERGE does not support targetting updatable views or foreign tables, and RETURNING clauses are not allowed either. These limitations are likely fixable with sufficient effort. Rewrite rules are also not supported, but it's not clear that we'd want to support them. Author: Pavan Deolasee Author: Álvaro Herrera Author: Amit Langote Author: Simon Riggs Reviewed-by: Peter Eisentraut Reviewed-by: Andres Freund (earlier versions) Reviewed-by: Peter Geoghegan (earlier versions) Reviewed-by: Robert Haas (earlier versions) Reviewed-by: Japin Li Reviewed-by: Justin Pryzby Reviewed-by: Tomas Vondra Reviewed-by: Zhihong Yu Discussion: https://postgr.es/m/CANP8+jKitBSrB7oTgT9CY2i1ObfOt36z0XMraQc+Xrz8QB0nXA@mail.gmail.com Discussion: https://postgr.es/m/CAH2-WzkJdBuxj9PO=2QaO9-3h3xGbQPZ34kJH=HukRekwM-GZg@mail.gmail.com Discussion: https://postgr.es/m/20201231134736.GA25392@alvherre.pgsql --- src/backend/utils/adt/ruleutils.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'src/backend/utils/adt/ruleutils.c') diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c index df5c4865014..82dc849a301 100644 --- a/src/backend/utils/adt/ruleutils.c +++ b/src/backend/utils/adt/ruleutils.c @@ -4940,6 +4940,8 @@ set_deparse_plan(deparse_namespace *dpns, Plan *plan) * For a WorkTableScan, locate the parent RecursiveUnion plan node and use * that as INNER referent. * + * For MERGE, make the inner tlist point to the merge source tlist, which + * is same as the targetlist that the ModifyTable's source plan provides. * For ON CONFLICT .. UPDATE we just need the inner tlist to point to the * excluded expression's tlist. (Similar to the SubqueryScan we don't want * to reuse OUTER, it's used for RETURNING in some modify table cases, @@ -4959,7 +4961,12 @@ set_deparse_plan(deparse_namespace *dpns, Plan *plan) dpns->inner_plan = innerPlan(plan); if (IsA(plan, ModifyTable)) - dpns->inner_tlist = ((ModifyTable *) plan)->exclRelTlist; + { + if (((ModifyTable *) plan)->operation == CMD_MERGE) + dpns->inner_tlist = dpns->outer_plan->targetlist; + else + dpns->inner_tlist = ((ModifyTable *) plan)->exclRelTlist; + } else if (dpns->inner_plan) dpns->inner_tlist = dpns->inner_plan->targetlist; else -- cgit v1.2.3