Rename GUC logical_decoding_mode to logical_replication_mode.

Rename the developer option 'logical_decoding_mode' to the more flexible
name 'logical_replication_mode' because doing so will make it easier to
extend this option in the future to help test other areas of logical
replication.

Currently, it is used on the publisher side to allow streaming or
serializing each change in logical decoding. In the upcoming patch, we are
planning to use it on the subscriber. On the subscriber, it will allow
serializing the changes to file and notifies the parallel apply workers to
read and apply them at the end of the transaction.

We discussed exposing this parameter as a subscription option but
it did not seem advisable since it is primarily used for testing/debugging
and there is no other such parameter. We also discussed having separate
GUCs for publisher and subscriber but for current testing/debugging
requirements, one GUC is sufficient.

Author: Hou Zhijie
Reviewed-by: Peter Smith, Kuroda Hayato, Sawada Masahiko, Amit Kapila
Discussion: https://postgr.es/m/CAD21AoAy2c=Mx=FTCs+EwUsf2kQL5MmU3N18X84k0EmCXntK4g@mail.gmail.com
Discussion: https://postgr.es/m/CAA4eK1+wyN6zpaHUkCLorEWNx75MG0xhMwcFhvjqm2KURZEAGw@mail.gmail.com

doc/src/sgml/config.sgml

@@ -11693,16 +11693,16 @@ LOG:  CleanUpLock: deleting: lock(0xb7acd844) id(24688,24696,0,0,0,1)
       </listitem>
      </varlistentry>
 
-     <varlistentry id="guc-logical-decoding-mode" xreflabel="logical_decoding_mode">
+     <varlistentry id="guc-logical-replication-mode" xreflabel="logical_replication_mode">
-      <term><varname>logical_decoding_mode</varname> (<type>enum</type>)
+      <term><varname>logical_replication_mode</varname> (<type>enum</type>)
       <indexterm>
-       <primary><varname>logical_decoding_mode</varname> configuration parameter</primary>
+       <primary><varname>logical_replication_mode</varname> configuration parameter</primary>
       </indexterm>
       </term>
       <listitem>
        <para>
         Allows streaming or serializing changes immediately in logical decoding.
-        The allowed values of <varname>logical_decoding_mode</varname> are
+        The allowed values of <varname>logical_replication_mode</varname> are
         <literal>buffered</literal> and <literal>immediate</literal>. When set
         to <literal>immediate</literal>, stream each change if
         <literal>streaming</literal> option (see optional parameters set by

src/backend/replication/logical/reorderbuffer.c

@@ -210,7 +210,7 @@ int			logical_decoding_work_mem;
 static const Size max_changes_in_memory = 4096; /* XXX for restore only */
 
 /* GUC variable */
-int			logical_decoding_mode = LOGICAL_DECODING_MODE_BUFFERED;
+int			logical_replication_mode = LOGICAL_REP_MODE_BUFFERED;
 
 /* ---------------------------------------
  * primary reorderbuffer support routines
@@ -3552,8 +3552,8 @@ ReorderBufferLargestStreamableTopTXN(ReorderBuffer *rb)
  * pick the largest (sub)transaction at-a-time to evict and spill its changes to
  * disk or send to the output plugin until we reach under the memory limit.
  *
- * If logical_decoding_mode is set to "immediate", stream or serialize the changes
+ * If logical_replication_mode is set to "immediate", stream or serialize the
- * immediately.
+ * changes immediately.
  *
  * XXX At this point we select the transactions until we reach under the memory
  * limit, but we might also adapt a more elaborate eviction strategy - for example
@@ -3566,15 +3566,15 @@ ReorderBufferCheckMemoryLimit(ReorderBuffer *rb)
 	ReorderBufferTXN *txn;
 
 	/*
-	 * Bail out if logical_decoding_mode is buffered and we haven't exceeded
+	 * Bail out if logical_replication_mode is buffered and we haven't exceeded
 	 * the memory limit.
 	 */
-	if (logical_decoding_mode == LOGICAL_DECODING_MODE_BUFFERED &&
+	if (logical_replication_mode == LOGICAL_REP_MODE_BUFFERED &&
 		rb->size < logical_decoding_work_mem * 1024L)
 		return;
 
 	/*
-	 * If logical_decoding_mode is immediate, loop until there's no change.
+	 * If logical_replication_mode is immediate, loop until there's no change.
 	 * Otherwise, loop until we reach under the memory limit. One might think
 	 * that just by evicting the largest (sub)transaction we will come under
 	 * the memory limit based on assumption that the selected transaction is
@@ -3584,7 +3584,7 @@ ReorderBufferCheckMemoryLimit(ReorderBuffer *rb)
 	 * change.
 	 */
 	while (rb->size >= logical_decoding_work_mem * 1024L ||
-		   (logical_decoding_mode == LOGICAL_DECODING_MODE_IMMEDIATE &&
+		   (logical_replication_mode == LOGICAL_REP_MODE_IMMEDIATE &&
 			rb->size > 0))
 	{
 		/*

src/backend/utils/misc/guc_tables.c

@@ -395,9 +395,9 @@ static const struct config_enum_entry ssl_protocol_versions_info[] = {
 	{NULL, 0, false}
 };
 
-static const struct config_enum_entry logical_decoding_mode_options[] = {
+static const struct config_enum_entry logical_replication_mode_options[] = {
-	{"buffered", LOGICAL_DECODING_MODE_BUFFERED, false},
+	{"buffered", LOGICAL_REP_MODE_BUFFERED, false},
-	{"immediate", LOGICAL_DECODING_MODE_IMMEDIATE, false},
+	{"immediate", LOGICAL_REP_MODE_IMMEDIATE, false},
 	{NULL, 0, false}
 };
 
@@ -4919,13 +4919,13 @@ struct config_enum ConfigureNamesEnum[] =
 	},
 
 	{
-		{"logical_decoding_mode", PGC_USERSET, DEVELOPER_OPTIONS,
+		{"logical_replication_mode", PGC_USERSET, DEVELOPER_OPTIONS,
-			gettext_noop("Allows streaming or serializing each change in logical decoding."),
+			gettext_noop("Controls when to replicate each change."),
-			NULL,
+			gettext_noop("On the publisher, it allows streaming or serializing each change in logical decoding."),
 			GUC_NOT_IN_SAMPLE
 		},
-		&logical_decoding_mode,
+		&logical_replication_mode,
-		LOGICAL_DECODING_MODE_BUFFERED, logical_decoding_mode_options,
+		LOGICAL_REP_MODE_BUFFERED, logical_replication_mode_options,
 		NULL, NULL, NULL
 	},
 

src/include/replication/reorderbuffer.h

@@ -17,15 +17,16 @@
 #include "utils/snapshot.h"
 #include "utils/timestamp.h"
 
+/* GUC variables */
 extern PGDLLIMPORT int logical_decoding_work_mem;
-extern PGDLLIMPORT int logical_decoding_mode;
+extern PGDLLIMPORT int logical_replication_mode;
 
-/* possible values for logical_decoding_mode */
+/* possible values for logical_replication_mode */
 typedef enum
 {
-	LOGICAL_DECODING_MODE_BUFFERED,
+	LOGICAL_REP_MODE_BUFFERED,
-	LOGICAL_DECODING_MODE_IMMEDIATE
+	LOGICAL_REP_MODE_IMMEDIATE
-} LogicalDecodingMode;
+} LogicalRepMode;
 
 /* an individual tuple, stored in one chunk of memory */
 typedef struct ReorderBufferTupleBuf

src/test/subscription/t/016_stream_subxact.pl

@@ -79,7 +79,7 @@ sub test_streaming
 my $node_publisher = PostgreSQL::Test::Cluster->new('publisher');
 $node_publisher->init(allows_streaming => 'logical');
 $node_publisher->append_conf('postgresql.conf',
-	'logical_decoding_mode = immediate');
+	'logical_replication_mode = immediate');
 $node_publisher->start;
 
 # Create subscriber node

src/test/subscription/t/018_stream_subxact_abort.pl

@@ -130,7 +130,7 @@ sub test_streaming
 my $node_publisher = PostgreSQL::Test::Cluster->new('publisher');
 $node_publisher->init(allows_streaming => 'logical');
 $node_publisher->append_conf('postgresql.conf',
-	'logical_decoding_mode = immediate');
+	'logical_replication_mode = immediate');
 $node_publisher->start;
 
 # Create subscriber node

src/test/subscription/t/019_stream_subxact_ddl_abort.pl

@@ -16,7 +16,7 @@ use Test::More;
 my $node_publisher = PostgreSQL::Test::Cluster->new('publisher');
 $node_publisher->init(allows_streaming => 'logical');
 $node_publisher->append_conf('postgresql.conf',
-	'logical_decoding_mode = immediate');
+	'logical_replication_mode = immediate');
 $node_publisher->start;
 
 # Create subscriber node

src/test/subscription/t/023_twophase_stream.pl

@@ -301,7 +301,7 @@ $node_publisher->init(allows_streaming => 'logical');
 $node_publisher->append_conf(
 	'postgresql.conf', qq(
 max_prepared_transactions = 10
-logical_decoding_mode = immediate
+logical_replication_mode = immediate
 ));
 $node_publisher->start;
 

src/tools/pgindent/typedefs.list

@@ -1458,7 +1458,6 @@ LogicalDecodeStreamStopCB
 LogicalDecodeStreamTruncateCB
 LogicalDecodeTruncateCB
 LogicalDecodingContext
-LogicalDecodingMode
 LogicalErrorCallbackState
 LogicalOutputPluginInit
 LogicalOutputPluginWriterPrepareWrite
@@ -1468,6 +1467,7 @@ LogicalRepBeginData
 LogicalRepCommitData
 LogicalRepCommitPreparedTxnData
 LogicalRepCtxStruct
+LogicalRepMode
 LogicalRepMsgType
 LogicalRepPartMapEntry
 LogicalRepPreparedTxnData