Fix replication with replica identity full

The comparison with the target rows on the subscriber side was done with
datumIsEqual(), which can have false negatives.  For instance, it didn't
work reliably for text columns.  So use the equality operator provided
by the type cache instead.

Also add more user documentation about replica identity requirements.
Reported-by: Tatsuo Ishii <ishii@sraoss.co.jp>

doc/src/sgml/logical-replication.sgml

@@ -110,11 +110,29 @@
    Publications can choose to limit the changes they produce to
    any combination of <command>INSERT</command>, <command>UPDATE</command>, and
    <command>DELETE</command>, similar to how triggers are fired by
-   particular event types.  If a table without a <literal>REPLICA
-   IDENTITY</literal> is added to a publication that
-   replicates <command>UPDATE</command> or <command>DELETE</command>
-   operations then subsequent <command>UPDATE</command>
-   or <command>DELETE</command> operations will fail on the publisher.
+   particular event types.  By default, all operation types are replicated.
+  </para>
+
+  <para>
+   A published table must have a <quote>replica identity</quote> configured in
+   order to be able to replicate <command>UPDATE</command>
+   and <command>DELETE</command> operations, so that appropriate rows to
+   update or delete can be identified on the subscriber side.  By default,
+   this is the primary key, if there is one.  Another unique index (with
+   certain additional requirements) can also be set to be the replica
+   identity.  If the table does not have any suitable key, then it can be set
+   to replica identity <quote>full</quote>, which means the entire row becomes
+   the key.  This, however, is very inefficient and should only be used as a
+   fallback if no other solution is possible.  If a replica identity other
+   than <quote>full</quote> is set on the publisher side, a replica identity
+   comprising the same or fewer columns must also be set on the subscriber
+   side.  See <xref linkend="SQL-CREATETABLE-REPLICA-IDENTITY"> for details on
+   how to set the replica identity.  If a table without a replica identity is
+   added to a publication that replicates <command>UPDATE</command>
+   or <command>DELETE</command> operations then
+   subsequent <command>UPDATE</command> or <command>DELETE</command>
+   operations will cause an error on the publisher.  <command>INSERT</command>
+   operations can proceed regardless of any replica identity.
   </para>
 
   <para>

src/backend/executor/execReplication.c

@@ -24,12 +24,14 @@
 #include "parser/parsetree.h"
 #include "storage/bufmgr.h"
 #include "storage/lmgr.h"
+#include "utils/builtins.h"
 #include "utils/datum.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
 #include "utils/snapmgr.h"
 #include "utils/syscache.h"
+#include "utils/typcache.h"
 #include "utils/tqual.h"
 
 
@@ -224,13 +226,15 @@ tuple_equals_slot(TupleDesc desc, HeapTuple tup, TupleTableSlot *slot)
 	Datum		values[MaxTupleAttributeNumber];
 	bool		isnull[MaxTupleAttributeNumber];
 	int			attrnum;
-	Form_pg_attribute att;
 
 	heap_deform_tuple(tup, desc, values, isnull);
 
 	/* Check equality of the attributes. */
 	for (attrnum = 0; attrnum < desc->natts; attrnum++)
 	{
+		Form_pg_attribute att;
+		TypeCacheEntry *typentry;
+
 		/*
 		 * If one value is NULL and other is not, then they are certainly not
 		 * equal
@@ -245,8 +249,17 @@ tuple_equals_slot(TupleDesc desc, HeapTuple tup, TupleTableSlot *slot)
 			continue;
 
 		att = desc->attrs[attrnum];
-		if (!datumIsEqual(values[attrnum], slot->tts_values[attrnum],
-						  att->attbyval, att->attlen))
+
+		typentry = lookup_type_cache(att->atttypid, TYPECACHE_EQ_OPR_FINFO);
+		if (!OidIsValid(typentry->eq_opr_finfo.fn_oid))
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_FUNCTION),
+					 errmsg("could not identify an equality operator for type %s",
+							format_type_be(att->atttypid))));
+
+		if (!DatumGetBool(FunctionCall2(&typentry->eq_opr_finfo,
+										values[attrnum],
+										slot->tts_values[attrnum])))
 			return false;
 	}
 

src/test/subscription/t/001_rep_changes.pl

@@ -3,7 +3,7 @@ use strict;
 use warnings;
 use PostgresNode;
 use TestLib;
-use Test::More tests => 15;
+use Test::More tests => 16;
 
 # Initialize publisher node
 my $node_publisher = get_new_node('publisher');
@@ -22,6 +22,10 @@ $node_publisher->safe_psql('postgres',
 	"CREATE TABLE tab_ins AS SELECT generate_series(1,1002) AS a");
 $node_publisher->safe_psql('postgres',
 	"CREATE TABLE tab_full AS SELECT generate_series(1,10) AS a");
+$node_publisher->safe_psql('postgres',
+	"CREATE TABLE tab_full2 (x text)");
+$node_publisher->safe_psql('postgres',
+	"INSERT INTO tab_full2 VALUES ('a'), ('b'), ('b')");
 $node_publisher->safe_psql('postgres',
 	"CREATE TABLE tab_rep (a int primary key)");
 $node_publisher->safe_psql('postgres',
@@ -33,6 +37,7 @@ $node_publisher->safe_psql('postgres',
 $node_subscriber->safe_psql('postgres', "CREATE TABLE tab_notrep (a int)");
 $node_subscriber->safe_psql('postgres', "CREATE TABLE tab_ins (a int)");
 $node_subscriber->safe_psql('postgres', "CREATE TABLE tab_full (a int)");
+$node_subscriber->safe_psql('postgres', "CREATE TABLE tab_full2 (x text)");
 $node_subscriber->safe_psql('postgres',
 	"CREATE TABLE tab_rep (a int primary key)");
 # different column count and order than on publisher
@@ -45,7 +50,7 @@ $node_publisher->safe_psql('postgres', "CREATE PUBLICATION tap_pub");
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION tap_pub_ins_only WITH (publish = insert)");
 $node_publisher->safe_psql('postgres',
-	"ALTER PUBLICATION tap_pub ADD TABLE tab_rep, tab_full, tab_mixed");
+	"ALTER PUBLICATION tap_pub ADD TABLE tab_rep, tab_full, tab_full2, tab_mixed");
 $node_publisher->safe_psql('postgres',
 	"ALTER PUBLICATION tap_pub_ins_only ADD TABLE tab_ins");
 
@@ -108,13 +113,18 @@ $node_publisher->safe_psql('postgres',
 	"ALTER TABLE tab_full REPLICA IDENTITY FULL");
 $node_subscriber->safe_psql('postgres',
 	"ALTER TABLE tab_full REPLICA IDENTITY FULL");
+$node_publisher->safe_psql('postgres',
+	"ALTER TABLE tab_full2 REPLICA IDENTITY FULL");
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE tab_full2 REPLICA IDENTITY FULL");
 $node_publisher->safe_psql('postgres',
 	"ALTER TABLE tab_ins REPLICA IDENTITY FULL");
 $node_subscriber->safe_psql('postgres',
 	"ALTER TABLE tab_ins REPLICA IDENTITY FULL");
 
-# and do the update
+# and do the updates
 $node_publisher->safe_psql('postgres', "UPDATE tab_full SET a = a * a");
+$node_publisher->safe_psql('postgres', "UPDATE tab_full2 SET x = 'bb' WHERE x = 'b'");
 
 # Wait for subscription to catch up
 $node_publisher->poll_query_until('postgres', $caughtup_query)
@@ -125,6 +135,13 @@ $result = $node_subscriber->safe_psql('postgres',
 is($result, qq(20|1|100),
 	'update works with REPLICA IDENTITY FULL and duplicate tuples');
 
+$result = $node_subscriber->safe_psql('postgres',
+	"SELECT x FROM tab_full2 ORDER BY 1");
+is($result, qq(a
+bb
+bb),
+	'update works with REPLICA IDENTITY FULL and text datums');
+
 # check that change of connection string and/or publication list causes
 # restart of subscription workers. Not all of these are registered as tests
 # as we need to poll for a change but the test suite will fail none the less