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/parser/parse_relation.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) (limited to 'src/backend/parser/parse_relation.c') diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c index cb9e177b5e5..7efa5f15d72 100644 --- a/src/backend/parser/parse_relation.c +++ b/src/backend/parser/parse_relation.c @@ -701,6 +701,17 @@ scanNSItemForColumn(ParseState *pstate, ParseNamespaceItem *nsitem, colname), parser_errposition(pstate, location))); + /* + * In a MERGE WHEN condition, no system column is allowed except tableOid + */ + if (pstate->p_expr_kind == EXPR_KIND_MERGE_WHEN && + attnum < InvalidAttrNumber && attnum != TableOidAttributeNumber) + ereport(ERROR, + (errcode(ERRCODE_INVALID_COLUMN_REFERENCE), + errmsg("cannot use system column \"%s\" in MERGE WHEN condition", + colname), + parser_errposition(pstate, location))); + /* Found a valid match, so build a Var */ if (attnum > InvalidAttrNumber) { @@ -3095,11 +3106,12 @@ expandNSItemVars(ParseNamespaceItem *nsitem, * for the attributes of the nsitem * * pstate->p_next_resno determines the resnos assigned to the TLEs. - * The referenced columns are marked as requiring SELECT access. + * The referenced columns are marked as requiring SELECT access, if + * caller requests that. */ List * expandNSItemAttrs(ParseState *pstate, ParseNamespaceItem *nsitem, - int sublevels_up, int location) + int sublevels_up, bool require_col_privs, int location) { RangeTblEntry *rte = nsitem->p_rte; List *names, @@ -3133,8 +3145,11 @@ expandNSItemAttrs(ParseState *pstate, ParseNamespaceItem *nsitem, false); te_list = lappend(te_list, te); - /* Require read access to each column */ - markVarForSelectPriv(pstate, varnode); + if (require_col_privs) + { + /* Require read access to each column */ + markVarForSelectPriv(pstate, varnode); + } } Assert(name == NULL && var == NULL); /* lists not the same length? */ -- cgit v1.2.3