Support "COPY view FROM" for views with INSTEAD OF INSERT triggers.

We just pass the data to the INSTEAD trigger.

Haribabu Kommi, reviewed by Dilip Kumar

Patch: <CAJrrPGcSQkrNkO+4PhLm4B8UQQQmU9YVUuqmtgM=pmzMfxWaWQ@mail.gmail.com>

doc/src/sgml/ref/copy.sgml

@@ -395,9 +395,15 @@ COPY <replaceable class="parameter">count</replaceable>
   <title>Notes</title>
 
    <para>
-    <command>COPY</command> can only be used with plain tables, not
+    <command>COPY TO</command> can only be used with plain tables, not
     with views.  However, you can write <literal>COPY (SELECT * FROM
-    <replaceable class="parameter">viewname</replaceable>) TO ...</literal>.
+    <replaceable class="parameter">viewname</replaceable>) TO ...</literal>
+    to copy the current contents of a view.
+   </para>
+
+   <para>
+    <command>COPY FROM</command> can be used with plain tables and with views
+    that have <literal>INSTEAD OF INSERT</> triggers.
    </para>
 
    <para>

src/backend/commands/copy.c

@@ -864,8 +864,8 @@ DoCopy(ParseState *pstate, const CopyStmt *stmt, uint64 *processed)
 			 * statement.
 			 *
 			 * In the case that columns are specified in the attribute list,
-			 * create a ColumnRef and ResTarget for each column and add them to
-			 * the target list for the resulting SELECT statement.
+			 * create a ColumnRef and ResTarget for each column and add them
+			 * to the target list for the resulting SELECT statement.
 			 */
 			if (!stmt->attlist)
 			{
@@ -2269,13 +2269,21 @@ CopyFrom(CopyState cstate)
 
 	Assert(cstate->rel);
 
-	if (cstate->rel->rd_rel->relkind != RELKIND_RELATION)
+	/*
+	 * The target must be a plain relation or have an INSTEAD OF INSERT row
+	 * trigger.  (Currently, such triggers are only allowed on views, so we
+	 * only hint about them in the view case.)
+	 */
+	if (cstate->rel->rd_rel->relkind != RELKIND_RELATION &&
+		!(cstate->rel->trigdesc &&
+		  cstate->rel->trigdesc->trig_insert_instead_row))
 	{
 		if (cstate->rel->rd_rel->relkind == RELKIND_VIEW)
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 					 errmsg("cannot copy to view \"%s\"",
-							RelationGetRelationName(cstate->rel))));
+							RelationGetRelationName(cstate->rel)),
+					 errhint("To enable copying to a view, provide an INSTEAD OF INSERT trigger.")));
 		else if (cstate->rel->rd_rel->relkind == RELKIND_MATVIEW)
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -2495,6 +2503,14 @@ CopyFrom(CopyState cstate)
 		}
 
 		if (!skip_tuple)
+		{
+			if (resultRelInfo->ri_TrigDesc &&
+				resultRelInfo->ri_TrigDesc->trig_insert_instead_row)
+			{
+				/* Pass the data to the INSTEAD ROW INSERT trigger */
+				ExecIRInsertTriggers(estate, resultRelInfo, slot);
+			}
+			else
 			{
 				/* Check the constraints of the tuple */
 				if (cstate->rel->rd_att->constr)
@@ -2509,10 +2525,10 @@ CopyFrom(CopyState cstate)
 					bufferedTuplesSize += tuple->t_len;
 
 					/*
-				 * If the buffer filled up, flush it. Also flush if the total
-				 * size of all the tuples in the buffer becomes large, to
-				 * avoid using large amounts of memory for the buffers when
-				 * the tuples are exceptionally wide.
+					 * If the buffer filled up, flush it.  Also flush if the
+					 * total size of all the tuples in the buffer becomes
+					 * large, to avoid using large amounts of memory for the
+					 * buffer when the tuples are exceptionally wide.
 					 */
 					if (nBufferedTuples == MAX_BUFFERED_TUPLES ||
 						bufferedTuplesSize > 65535)
@@ -2533,8 +2549,11 @@ CopyFrom(CopyState cstate)
 					heap_insert(cstate->rel, tuple, mycid, hi_options, bistate);
 
 					if (resultRelInfo->ri_NumIndices > 0)
-					recheckIndexes = ExecInsertIndexTuples(slot, &(tuple->t_self),
-														 estate, false, NULL,
+						recheckIndexes = ExecInsertIndexTuples(slot,
+															&(tuple->t_self),
+															   estate,
+															   false,
+															   NULL,
 															   NIL);
 
 					/* AFTER ROW INSERT Triggers */
@@ -2543,6 +2562,7 @@ CopyFrom(CopyState cstate)
 
 					list_free(recheckIndexes);
 				}
+			}
 
 			/*
 			 * We count only tuples not suppressed by a BEFORE INSERT trigger;

src/test/regress/expected/copy2.out

@@ -535,6 +535,29 @@ COPY rls_t1 (a, b) TO stdout;
 2	3
 4	1
 RESET SESSION AUTHORIZATION;
+-- test with INSTEAD OF INSERT trigger on a view
+CREATE TABLE instead_of_insert_tbl(id serial, name text);
+CREATE VIEW instead_of_insert_tbl_view AS SELECT ''::text AS str;
+COPY instead_of_insert_tbl_view FROM stdin; -- fail
+ERROR:  cannot copy to view "instead_of_insert_tbl_view"
+HINT:  To enable copying to a view, provide an INSTEAD OF INSERT trigger.
+CREATE FUNCTION fun_instead_of_insert_tbl() RETURNS trigger AS $$
+BEGIN
+  INSERT INTO instead_of_insert_tbl (name) VALUES (NEW.str);
+  RETURN NULL;
+END;
+$$ LANGUAGE plpgsql;
+CREATE TRIGGER trig_instead_of_insert_tbl_view
+  INSTEAD OF INSERT ON instead_of_insert_tbl_view
+  FOR EACH ROW EXECUTE PROCEDURE fun_instead_of_insert_tbl();
+COPY instead_of_insert_tbl_view FROM stdin;
+SELECT * FROM instead_of_insert_tbl;
+ id | name  
+----+-------
+  1 | test1
+(1 row)
+
+-- clean up
 DROP TABLE forcetest;
 DROP TABLE vistest;
 DROP FUNCTION truncate_in_subxact();
@@ -544,3 +567,6 @@ DROP ROLE regress_rls_copy_user;
 DROP ROLE regress_rls_copy_user_colperms;
 DROP FUNCTION fn_x_before();
 DROP FUNCTION fn_x_after();
+DROP TABLE instead_of_insert_tbl;
+DROP VIEW instead_of_insert_tbl_view;
+DROP FUNCTION fun_instead_of_insert_tbl();

src/test/regress/sql/copy2.sql

@@ -387,6 +387,32 @@ COPY rls_t1 (a, b) TO stdout;
 
 RESET SESSION AUTHORIZATION;
 
+-- test with INSTEAD OF INSERT trigger on a view
+CREATE TABLE instead_of_insert_tbl(id serial, name text);
+CREATE VIEW instead_of_insert_tbl_view AS SELECT ''::text AS str;
+
+COPY instead_of_insert_tbl_view FROM stdin; -- fail
+test1
+\.
+
+CREATE FUNCTION fun_instead_of_insert_tbl() RETURNS trigger AS $$
+BEGIN
+  INSERT INTO instead_of_insert_tbl (name) VALUES (NEW.str);
+  RETURN NULL;
+END;
+$$ LANGUAGE plpgsql;
+CREATE TRIGGER trig_instead_of_insert_tbl_view
+  INSTEAD OF INSERT ON instead_of_insert_tbl_view
+  FOR EACH ROW EXECUTE PROCEDURE fun_instead_of_insert_tbl();
+
+COPY instead_of_insert_tbl_view FROM stdin;
+test1
+\.
+
+SELECT * FROM instead_of_insert_tbl;
+
+
+-- clean up
 DROP TABLE forcetest;
 DROP TABLE vistest;
 DROP FUNCTION truncate_in_subxact();
@@ -396,3 +422,6 @@ DROP ROLE regress_rls_copy_user;
 DROP ROLE regress_rls_copy_user_colperms;
 DROP FUNCTION fn_x_before();
 DROP FUNCTION fn_x_after();
+DROP TABLE instead_of_insert_tbl;
+DROP VIEW instead_of_insert_tbl_view;
+DROP FUNCTION fun_instead_of_insert_tbl();