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/commands/explain.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) (limited to 'src/backend/commands/explain.c') diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c index 9f632285b62..cb13227db1f 100644 --- a/src/backend/commands/explain.c +++ b/src/backend/commands/explain.c @@ -1188,6 +1188,9 @@ ExplainNode(PlanState *planstate, List *ancestors, case CMD_DELETE: pname = operation = "Delete"; break; + case CMD_MERGE: + pname = operation = "Merge"; + break; default: pname = "???"; break; @@ -3877,6 +3880,11 @@ show_modifytable_info(ModifyTableState *mtstate, List *ancestors, operation = "Delete"; foperation = "Foreign Delete"; break; + case CMD_MERGE: + operation = "Merge"; + /* XXX unsupported for now, but avoid compiler noise */ + foperation = "Foreign Merge"; + break; default: operation = "???"; foperation = "Foreign ???"; @@ -3999,6 +4007,33 @@ show_modifytable_info(ModifyTableState *mtstate, List *ancestors, other_path, 0, es); } } + else if (node->operation == CMD_MERGE) + { + /* EXPLAIN ANALYZE display of tuples processed */ + if (es->analyze && mtstate->ps.instrument) + { + double total; + double insert_path; + double update_path; + double delete_path; + double skipped_path; + + InstrEndLoop(outerPlanState(mtstate)->instrument); + + /* count the number of source rows */ + total = outerPlanState(mtstate)->instrument->ntuples; + insert_path = mtstate->mt_merge_inserted; + update_path = mtstate->mt_merge_updated; + delete_path = mtstate->mt_merge_deleted; + skipped_path = total - insert_path - update_path - delete_path; + Assert(skipped_path >= 0); + + ExplainPropertyFloat("Tuples Inserted", NULL, insert_path, 0, es); + ExplainPropertyFloat("Tuples Updated", NULL, update_path, 0, es); + ExplainPropertyFloat("Tuples Deleted", NULL, delete_path, 0, es); + ExplainPropertyFloat("Tuples Skipped", NULL, skipped_path, 0, es); + } + } if (labeltargets) ExplainCloseGroup("Target Tables", "Target Tables", false, es); -- cgit v1.2.3