Add support for INSERT ... ON CONFLICT DO NOTHING/UPDATE.

The newly added ON CONFLICT clause allows to specify an alternative to
raising a unique or exclusion constraint violation error when inserting.
ON CONFLICT refers to constraints that can either be specified using a
inference clause (by specifying the columns of a unique constraint) or
by naming a unique or exclusion constraint.  DO NOTHING avoids the
constraint violation, without touching the pre-existing row.  DO UPDATE
SET ... [WHERE ...] updates the pre-existing tuple, and has access to
both the tuple proposed for insertion and the existing tuple; the
optional WHERE clause can be used to prevent an update from being
executed.  The UPDATE SET and WHERE clauses have access to the tuple
proposed for insertion using the "magic" EXCLUDED alias, and to the
pre-existing tuple using the table name or its alias.

This feature is often referred to as upsert.

This is implemented using a new infrastructure called "speculative
insertion". It is an optimistic variant of regular insertion that first
does a pre-check for existing tuples and then attempts an insert.  If a
violating tuple was inserted concurrently, the speculatively inserted
tuple is deleted and a new attempt is made.  If the pre-check finds a
matching tuple the alternative DO NOTHING or DO UPDATE action is taken.
If the insertion succeeds without detecting a conflict, the tuple is
deemed inserted.

To handle the possible ambiguity between the excluded alias and a table
named excluded, and for convenience with long relation names, INSERT
INTO now can alias its target table.

Bumps catversion as stored rules change.

Author: Peter Geoghegan, with significant contributions from Heikki
    Linnakangas and Andres Freund. Testing infrastructure by Jeff Janes.
Reviewed-By: Heikki Linnakangas, Andres Freund, Robert Haas, Simon Riggs,
    Dean Rasheed, Stephen Frost and many others.

contrib/pg_stat_statements/pg_stat_statements.c

@@ -2264,6 +2264,7 @@ JumbleQuery(pgssJumbleState *jstate, Query *query)
 	JumbleRangeTable(jstate, query->rtable);
 	JumbleExpr(jstate, (Node *) query->jointree);
 	JumbleExpr(jstate, (Node *) query->targetList);
+	JumbleExpr(jstate, (Node *) query->onConflict);
 	JumbleExpr(jstate, (Node *) query->returningList);
 	JumbleExpr(jstate, (Node *) query->groupClause);
 	JumbleExpr(jstate, query->havingQual);
@@ -2631,6 +2632,16 @@ JumbleExpr(pgssJumbleState *jstate, Node *node)
 				APP_JUMB(ce->cursor_param);
 			}
 			break;
+		case T_InferenceElem:
+			{
+				InferenceElem *ie = (InferenceElem *) node;
+
+				APP_JUMB(ie->infercollid);
+				APP_JUMB(ie->inferopfamily);
+				APP_JUMB(ie->inferopcinputtype);
+				JumbleExpr(jstate, ie->expr);
+			}
+			break;
 		case T_TargetEntry:
 			{
 				TargetEntry *tle = (TargetEntry *) node;
@@ -2667,6 +2678,20 @@ JumbleExpr(pgssJumbleState *jstate, Node *node)
 				JumbleExpr(jstate, from->quals);
 			}
 			break;
+		case T_OnConflictExpr:
+			{
+				OnConflictExpr   *conf = (OnConflictExpr *) node;
+
+				APP_JUMB(conf->action);
+				JumbleExpr(jstate, (Node *) conf->arbiterElems);
+				JumbleExpr(jstate, conf->arbiterWhere);
+				JumbleExpr(jstate, (Node  *) conf->onConflictSet);
+				JumbleExpr(jstate, conf->onConflictWhere);
+				APP_JUMB(conf->constraint);
+				APP_JUMB(conf->exclRelIndex);
+				JumbleExpr(jstate, (Node  *) conf->exclRelTlist);
+			}
+			break;
 		case T_List:
 			foreach(temp, (List *) node)
 			{

contrib/postgres_fdw/deparse.c

@@ -847,8 +847,8 @@ appendWhereClause(StringInfo buf,
 void
 deparseInsertSql(StringInfo buf, PlannerInfo *root,
 				 Index rtindex, Relation rel,
-				 List *targetAttrs, List *returningList,
-				 List **retrieved_attrs)
+				 List *targetAttrs, bool doNothing,
+				 List *returningList, List **retrieved_attrs)
 {
 	AttrNumber	pindex;
 	bool		first;
@@ -892,6 +892,9 @@ deparseInsertSql(StringInfo buf, PlannerInfo *root,
 	else
 		appendStringInfoString(buf, " DEFAULT VALUES");
 
+	if (doNothing)
+		appendStringInfoString(buf, " ON CONFLICT DO NOTHING");
+
 	deparseReturningList(buf, root, rtindex, rel,
 					   rel->trigdesc && rel->trigdesc->trig_insert_after_row,
 						 returningList, retrieved_attrs);

contrib/postgres_fdw/expected/postgres_fdw.out

@@ -2327,6 +2327,11 @@ INSERT INTO ft1(c1, c2) VALUES(11, 12);  -- duplicate key
 ERROR:  duplicate key value violates unique constraint "t1_pkey"
 DETAIL:  Key ("C 1")=(11) already exists.
 CONTEXT:  Remote SQL command: INSERT INTO "S 1"."T 1"("C 1", c2, c3, c4, c5, c6, c7, c8) VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
+INSERT INTO ft1(c1, c2) VALUES(11, 12) ON CONFLICT DO NOTHING; -- works
+INSERT INTO ft1(c1, c2) VALUES(11, 12) ON CONFLICT (c1, c2) DO NOTHING; -- unsupported
+ERROR:  there is no unique or exclusion constraint matching the ON CONFLICT specification
+INSERT INTO ft1(c1, c2) VALUES(11, 12) ON CONFLICT (c1, c2) DO UPDATE SET c3 = 'ffg'; -- unsupported
+ERROR:  there is no unique or exclusion constraint matching the ON CONFLICT specification
 INSERT INTO ft1(c1, c2) VALUES(1111, -2);  -- c2positive
 ERROR:  new row for relation "T 1" violates check constraint "c2positive"
 DETAIL:  Failing row contains (1111, -2, null, null, null, null, ft1       , null).

contrib/postgres_fdw/postgres_fdw.c

@@ -1171,6 +1171,7 @@ postgresPlanForeignModify(PlannerInfo *root,
 	List	   *targetAttrs = NIL;
 	List	   *returningList = NIL;
 	List	   *retrieved_attrs = NIL;
+	bool		doNothing = false;
 
 	initStringInfo(&sql);
 
@@ -1222,14 +1223,26 @@ postgresPlanForeignModify(PlannerInfo *root,
 	if (plan->returningLists)
 		returningList = (List *) list_nth(plan->returningLists, subplan_index);
 
+	/*
+	 * ON CONFLICT DO UPDATE and DO NOTHING case with inference specification
+	 * should have already been rejected in the optimizer, as presently there
+	 * is no way to recognize an arbiter index on a foreign table.  Only DO
+	 * NOTHING is supported without an inference specification.
+	 */
+	if (plan->onConflictAction == ONCONFLICT_NOTHING)
+		doNothing = true;
+	else if (plan->onConflictAction != ONCONFLICT_NONE)
+		elog(ERROR, "unexpected ON CONFLICT specification: %d",
+			 (int) plan->onConflictAction);
+
 	/*
 	 * Construct the SQL command string.
 	 */
 	switch (operation)
 	{
 		case CMD_INSERT:
 			deparseInsertSql(&sql, root, resultRelation, rel,
-							 targetAttrs, returningList,
+							 targetAttrs, doNothing, returningList,
 							 &retrieved_attrs);
 			break;
 		case CMD_UPDATE:

contrib/postgres_fdw/postgres_fdw.h

@@ -60,7 +60,7 @@ extern void appendWhereClause(StringInfo buf,
 				  List **params);
 extern void deparseInsertSql(StringInfo buf, PlannerInfo *root,
 				 Index rtindex, Relation rel,
-				 List *targetAttrs, List *returningList,
+				 List *targetAttrs, bool doNothing, List *returningList,
 				 List **retrieved_attrs);
 extern void deparseUpdateSql(StringInfo buf, PlannerInfo *root,
 				 Index rtindex, Relation rel,

contrib/postgres_fdw/sql/postgres_fdw.sql

@@ -372,6 +372,9 @@ UPDATE ft2 SET c2 = c2 + 600 WHERE c1 % 10 = 8 AND c1 < 1200 RETURNING *;
 ALTER TABLE "S 1"."T 1" ADD CONSTRAINT c2positive CHECK (c2 >= 0);
 
 INSERT INTO ft1(c1, c2) VALUES(11, 12);  -- duplicate key
+INSERT INTO ft1(c1, c2) VALUES(11, 12) ON CONFLICT DO NOTHING; -- works
+INSERT INTO ft1(c1, c2) VALUES(11, 12) ON CONFLICT (c1, c2) DO NOTHING; -- unsupported
+INSERT INTO ft1(c1, c2) VALUES(11, 12) ON CONFLICT (c1, c2) DO UPDATE SET c3 = 'ffg'; -- unsupported
 INSERT INTO ft1(c1, c2) VALUES(1111, -2);  -- c2positive
 UPDATE ft1 SET c2 = -c2 WHERE c1 = 1;  -- c2positive
 

contrib/test_decoding/expected/ddl.out

@@ -148,6 +148,24 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'inc
  COMMIT
 (9 rows)
 
+-- ON CONFLICT DO UPDATE support
+BEGIN;
+INSERT INTO replication_example(id, somedata, somenum) SELECT i, i, i FROM generate_series(-15, 15) i
+  ON CONFLICT (id) DO UPDATE SET somenum = excluded.somenum + 1;
+COMMIT;
+/* display results, but hide most of the output */
+SELECT count(*), min(data), max(data)
+FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1')
+GROUP BY substring(data, 1, 40)
+ORDER BY 1,2;
+ count |                                                                     min                                                                      |                                                                      max                                                                      
+-------+----------------------------------------------------------------------------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------------
+     1 | BEGIN                                                                                                                                        | BEGIN
+     1 | COMMIT                                                                                                                                       | COMMIT
+    15 | table public.replication_example: UPDATE: id[integer]:10 somedata[integer]:4 somenum[integer]:11 zaphod1[integer]:null zaphod2[integer]:null | table public.replication_example: UPDATE: id[integer]:9 somedata[integer]:3 somenum[integer]:10 zaphod1[integer]:null zaphod2[integer]:null
+    16 | table public.replication_example: INSERT: id[integer]:0 somedata[integer]:0 somenum[integer]:0 zaphod1[integer]:null zaphod2[integer]:null   | table public.replication_example: INSERT: id[integer]:-9 somedata[integer]:-9 somenum[integer]:-9 zaphod1[integer]:null zaphod2[integer]:null
+(4 rows)
+
 -- hide changes bc of oid visible in full table rewrites
 CREATE TABLE tr_unique(id2 serial unique NOT NULL, data int);
 INSERT INTO tr_unique(data) VALUES(10);
@@ -196,6 +214,22 @@ ORDER BY 1,2;
  20467 | table public.tr_etoomuch: DELETE: id[integer]:1 | table public.tr_etoomuch: UPDATE: id[integer]:9999 data[integer]:-9999
 (3 rows)
 
+-- check that a large, spooled, upsert works
+INSERT INTO tr_etoomuch (id, data)
+SELECT g.i, -g.i FROM generate_series(8000, 12000) g(i)
+ON CONFLICT(id) DO UPDATE SET data = EXCLUDED.data;
+SELECT substring(data, 1, 29), count(*)
+FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1')
+GROUP BY 1
+ORDER BY min(location - '0/0');
+           substring           | count 
+-------------------------------+-------
+ BEGIN                         |     1
+ table public.tr_etoomuch: UPD |  2235
+ table public.tr_etoomuch: INS |  1766
+ COMMIT                        |     1
+(4 rows)
+
 /*
  * check whether we decode subtransactions correctly in relation with each
  * other

contrib/test_decoding/expected/toast.out

@@ -23,6 +23,10 @@ INSERT INTO xpto (toasted_col2) SELECT repeat(string_agg(to_char(g.i, 'FM0000'),
 -- update of existing column
 UPDATE xpto SET toasted_col1 = (SELECT string_agg(g.i::text, '') FROM generate_series(1, 2000) g(i)) WHERE id = 1;
 UPDATE xpto SET rand1 = 123.456 WHERE id = 1;
+-- updating external via INSERT ... ON CONFLICT DO UPDATE
+INSERT INTO xpto(id, toasted_col2) VALUES (2, 'toasted2-upsert')
+ON CONFLICT (id)
+DO UPDATE SET toasted_col2 = EXCLUDED.toasted_col2 || xpto.toasted_col2;
 DELETE FROM xpto WHERE id = 1;
 DROP TABLE IF EXISTS toasted_key;
 NOTICE:  table "toasted_key" does not exist, skipping
@@ -64,6 +68,9 @@ SELECT substr(data, 1, 200) FROM pg_logical_slot_get_changes('regression_slot',
  table public.xpto: UPDATE: id[integer]:1 toasted_col1[text]:unchanged-toast-datum rand1[double precision]:123.456 toasted_col2[text]:unchanged-toast-datum rand2[double precision]:1578
  COMMIT
  BEGIN
+ table public.xpto: UPDATE: id[integer]:2 toasted_col1[text]:null rand1[double precision]:3077 toasted_col2[text]:'toasted2-upsert00010002000300040005000600070008000900100011001200130014001500160017001
+ COMMIT
+ BEGIN
  table public.xpto: DELETE: id[integer]:1
  COMMIT
  BEGIN
@@ -283,7 +290,7 @@ SELECT substr(data, 1, 200) FROM pg_logical_slot_get_changes('regression_slot',
  table public.toasted_copy: INSERT: id[integer]:202 data[text]:'untoasted199'
  table public.toasted_copy: INSERT: id[integer]:203 data[text]:'untoasted200'
  COMMIT
-(232 rows)
+(235 rows)
 
 SELECT pg_drop_replication_slot('regression_slot');
  pg_drop_replication_slot 

contrib/test_decoding/sql/ddl.sql

@@ -84,6 +84,18 @@ COMMIT;
 -- show changes
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
+-- ON CONFLICT DO UPDATE support
+BEGIN;
+INSERT INTO replication_example(id, somedata, somenum) SELECT i, i, i FROM generate_series(-15, 15) i
+  ON CONFLICT (id) DO UPDATE SET somenum = excluded.somenum + 1;
+COMMIT;
+
+/* display results, but hide most of the output */
+SELECT count(*), min(data), max(data)
+FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1')
+GROUP BY substring(data, 1, 40)
+ORDER BY 1,2;
+
 -- hide changes bc of oid visible in full table rewrites
 CREATE TABLE tr_unique(id2 serial unique NOT NULL, data int);
 INSERT INTO tr_unique(data) VALUES(10);
@@ -114,6 +126,16 @@ FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids',
 GROUP BY substring(data, 1, 24)
 ORDER BY 1,2;
 
+-- check that a large, spooled, upsert works
+INSERT INTO tr_etoomuch (id, data)
+SELECT g.i, -g.i FROM generate_series(8000, 12000) g(i)
+ON CONFLICT(id) DO UPDATE SET data = EXCLUDED.data;
+
+SELECT substring(data, 1, 29), count(*)
+FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1')
+GROUP BY 1
+ORDER BY min(location - '0/0');
+
 /*
  * check whether we decode subtransactions correctly in relation with each
  * other

contrib/test_decoding/sql/toast.sql

@@ -25,6 +25,11 @@ UPDATE xpto SET toasted_col1 = (SELECT string_agg(g.i::text, '') FROM generate_s
 
 UPDATE xpto SET rand1 = 123.456 WHERE id = 1;
 
+-- updating external via INSERT ... ON CONFLICT DO UPDATE
+INSERT INTO xpto(id, toasted_col2) VALUES (2, 'toasted2-upsert')
+ON CONFLICT (id)
+DO UPDATE SET toasted_col2 = EXCLUDED.toasted_col2 || xpto.toasted_col2;
+
 DELETE FROM xpto WHERE id = 1;
 
 DROP TABLE IF EXISTS toasted_key;

doc/src/sgml/fdwhandler.sgml

@@ -1050,6 +1050,13 @@ GetForeignServerByName(const char *name, bool missing_ok);
      source provides.
     </para>
 
+    <para>
+     <command>INSERT</> with an <literal>ON CONFLICT</> clause does not
+     support specifying the conflict target, as remote constraints are not
+     locally known. This in turn implies that <literal>ON CONFLICT DO
+     UPDATE</> is not supported, since the specification is mandatory there.
+    </para>
+
   </sect1>
 
  </chapter>

doc/src/sgml/keywords.sgml

@@ -853,6 +853,13 @@
     <entry></entry>
     <entry></entry>
    </row>
+   <row>
+    <entry><token>CONFLICT</token></entry>
+    <entry>non-reserved</entry>
+    <entry></entry>
+    <entry></entry>
+    <entry></entry>
+   </row>
    <row>
     <entry><token>CONNECT</token></entry>
     <entry></entry>

doc/src/sgml/mvcc.sgml

@@ -326,8 +326,27 @@
    </para>
 
    <para>
-    Because of the above rule, it is possible for an updating command to see an
-    inconsistent snapshot: it can see the effects of concurrent updating
+    <command>INSERT</command> with an <literal>ON CONFLICT DO UPDATE</> clause
+    behaves similarly. In Read Committed mode, each row proposed for insertion
+    will either insert or update. Unless there are unrelated errors, one of
+    those two outcomes is guaranteed.  If a conflict originates in another
+    transaction whose effects are not yet visible to the <command>INSERT
+    </command>, the <command>UPDATE</command> clause will affect that row,
+    even though possibly <emphasis>no</> version of that row is
+    conventionally visible to the command.
+   </para>
+
+   <para>
+    <command>INSERT</command> with an <literal>ON CONFLICT DO
+    NOTHING</> clause may have insertion not proceed for a row due to
+    the outcome of another transaction whose effects are not visible
+    to the <command>INSERT</command> snapshot.  Again, this is only
+    the case in Read Committed mode.
+   </para>
+
+   <para>
+    Because of the above rules, it is possible for an updating command to see
+    an inconsistent snapshot: it can see the effects of concurrent updating
     commands on the same rows it is trying to update, but it
     does not see effects of those commands on other rows in the database.
     This behavior makes Read Committed mode unsuitable for commands that

doc/src/sgml/plpgsql.sgml

@@ -2623,7 +2623,11 @@ END;
     <para>
 
     This example uses exception handling to perform either
-    <command>UPDATE</> or <command>INSERT</>, as appropriate:
+    <command>UPDATE</> or <command>INSERT</>, as appropriate.  It is
+    recommended that applications use <command>INSERT</> with
+    <literal>ON CONFLICT DO UPDATE</> rather than actually using
+    this pattern.  This example serves primarily to illustrate use of
+    <application>PL/pgSQL</application> control flow structures:
 
 <programlisting>
 CREATE TABLE db (a INT PRIMARY KEY, b TEXT);
@@ -3852,9 +3856,11 @@ ASSERT <replaceable class="parameter">condition</replaceable> <optional> , <repl
     <command>INSERT</> and <command>UPDATE</> operations, the return value
     should be <varname>NEW</>, which the trigger function may modify to
     support <command>INSERT RETURNING</> and <command>UPDATE RETURNING</>
-    (this will also affect the row value passed to any subsequent triggers).
-    For <command>DELETE</> operations, the return value should be
-    <varname>OLD</>.
+    (this will also affect the row value passed to any subsequent triggers,
+    or passed to a special <varname>EXCLUDED</> alias reference within
+    an <command>INSERT</> statement with an <literal>ON CONFLICT DO
+    UPDATE</> clause).  For <command>DELETE</> operations, the return
+    value should be <varname>OLD</>.
    </para>
 
    <para>

doc/src/sgml/postgres-fdw.sgml

@@ -68,6 +68,14 @@
   in your user mapping must have privileges to do these things.)
  </para>
 
+ <para>
+  Note that <filename>postgres_fdw</> currently lacks support for
+  <command>INSERT</command> statements with an <literal>ON CONFLICT DO
+  UPDATE</> clause.  However, the <literal>ON CONFLICT DO NOTHING</>
+  clause is supported, provided a unique index inference specification
+  is omitted.
+ </para>
+
  <para>
   It is generally recommended that the columns of a foreign table be declared
   with exactly the same data types, and collations if applicable, as the

doc/src/sgml/protocol.sgml

@@ -2998,9 +2998,16 @@ CommandComplete (B)
         <literal>INSERT <replaceable>oid</replaceable>
         <replaceable>rows</replaceable></literal>, where
         <replaceable>rows</replaceable> is the number of rows
-        inserted. <replaceable>oid</replaceable> is the object ID
-        of the inserted row if <replaceable>rows</replaceable> is 1
-        and the target table has OIDs;
+        inserted. However, if and only if <literal>ON CONFLICT
+        UPDATE</> is specified, then the tag is <literal>UPSERT
+        <replaceable>oid</replaceable>
+        <replaceable>rows</replaceable></literal>, where
+        <replaceable>rows</replaceable> is the number of rows inserted
+        <emphasis>or updated</emphasis>.
+        <replaceable>oid</replaceable> is the object ID of the
+        inserted row if <replaceable>rows</replaceable> is 1 and the
+        target table has OIDs, and (for the <literal>UPSERT</literal>
+        tag), the row was actually inserted rather than updated;
         otherwise <replaceable>oid</replaceable> is 0.
        </para>