Add ability to reserve WAL upon slot creation via replication protocol.

Since 6fcd885 it is possible to immediately reserve WAL when creating a
slot via pg_create_physical_replication_slot(). Extend the replication
protocol to allow that as well.

Although, in contrast to the SQL interface, it is possible to update the
reserved location via the replication interface, it is still useful
being able to reserve upon creation there. Otherwise the logic in
ReplicationSlotReserveWal() has to be repeated in slot employing
clients.

Author: Michael Paquier
Discussion: CAB7nPqT0Wc1W5mdYGeJ_wbutbwNN+3qgrFR64avXaQCiJMGaYA@mail.gmail.com

diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 42e94971741a4bd6a390121cec3ec986a667427d..2caa84a12532cfca0eeae5eb425b51433c225e0c 100644 (file)
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -1434,7 +1434,7 @@ The commands accepted in walsender mode are:
   </varlistentry>
 
   <varlistentry>
-    <term>CREATE_REPLICATION_SLOT <replaceable class="parameter">slot_name</> { <literal>PHYSICAL</> | <literal>LOGICAL</> <replaceable class="parameter">output_plugin</> }
+    <term>CREATE_REPLICATION_SLOT <replaceable class="parameter">slot_name</> { <literal>PHYSICAL</> [ RESERVE_WAL ] | <literal>LOGICAL</> <replaceable class="parameter">output_plugin</> }
      <indexterm><primary>CREATE_REPLICATION_SLOT</primary></indexterm>
     </term>
     <listitem>
@@ -1463,6 +1463,17 @@ The commands accepted in walsender mode are:
          </para>
        </listitem>
       </varlistentry>
+
+      <varlistentry>
+       <term><literal>RESERVE_WAL</></term>
+       <listitem>
+        <para>
+         Specify that this physical replication reserves <acronym>WAL</>
+         immediately; otherwise <acronym>WAL</> is only reserved upon
+         connection from a streaming replication client.
+        </para>
+       </listitem>
+      </varlistentry>
      </variablelist>
     </listitem>
   </varlistentry>

diff --git a/src/backend/replication/repl_gram.y b/src/backend/replication/repl_gram.y
index e9177ca0db6d2596ec97a543764a919ed78c9593..1b7536442233bd552d8e69e9b98b4e97bfde071c 100644 (file)
--- a/src/backend/replication/repl_gram.y
+++ b/src/backend/replication/repl_gram.y
@@ -76,6 +76,7 @@ Node *replication_parse_result;
 %token K_PHYSICAL
 %token K_LOGICAL
 %token K_SLOT
+%token K_RESERVE_WAL
 
 %type <node>   command
 %type <node>   base_backup start_replication start_logical_replication
@@ -88,6 +89,7 @@ Node *replication_parse_result;
 %type <defelt> plugin_opt_elem
 %type <node>   plugin_opt_arg
 %type <str>        opt_slot
+%type <boolval>    opt_reserve_wal
 
 %%
 
@@ -181,13 +183,14 @@ base_backup_opt:
            ;
 
 create_replication_slot:
-           /* CREATE_REPLICATION_SLOT slot PHYSICAL */
-           K_CREATE_REPLICATION_SLOT IDENT K_PHYSICAL
+           /* CREATE_REPLICATION_SLOT slot PHYSICAL RESERVE_WAL */
+           K_CREATE_REPLICATION_SLOT IDENT K_PHYSICAL opt_reserve_wal
                {
                    CreateReplicationSlotCmd *cmd;
                    cmd = makeNode(CreateReplicationSlotCmd);
                    cmd->kind = REPLICATION_KIND_PHYSICAL;
                    cmd->slotname = $2;
+                   cmd->reserve_wal = $4;
                    $$ = (Node *) cmd;
                }
            /* CREATE_REPLICATION_SLOT slot LOGICAL plugin */
@@ -268,6 +271,11 @@ opt_physical:
            | /* EMPTY */
            ;
 
+opt_reserve_wal:
+           K_RESERVE_WAL                   { $$ = true; }
+           | /* EMPTY */                   { $$ = false; }
+           ;
+
 opt_slot:
            K_SLOT IDENT
                { $$ = $2; }

diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
index 91bac21b06b5607403b086322ed9a52aeb5b5a02..126e7d906400c432e17d298424be84e3f57a054b 100644 (file)
--- a/src/backend/replication/repl_scanner.l
+++ b/src/backend/replication/repl_scanner.l
@@ -95,6 +95,7 @@ CREATE_REPLICATION_SLOT       { return K_CREATE_REPLICATION_SLOT; }
 DROP_REPLICATION_SLOT      { return K_DROP_REPLICATION_SLOT; }
 TIMELINE_HISTORY   { return K_TIMELINE_HISTORY; }
 PHYSICAL           { return K_PHYSICAL; }
+RESERVE_WAL            { return K_RESERVE_WAL; }
 LOGICAL                { return K_LOGICAL; }
 SLOT               { return K_SLOT; }
 

diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 27de156b1ffb7c6d4b7f64bb57a93a4f21428c3a..c95fe75a7215151ec4049b9d6731c9b52c9c383d 100644 (file)
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -826,6 +826,14 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 
        ReplicationSlotPersist();
    }
+   else if (cmd->kind == REPLICATION_KIND_PHYSICAL && cmd->reserve_wal)
+   {
+       ReplicationSlotReserveWal();
+
+       /* Write this slot to disk */
+       ReplicationSlotMarkDirty();
+       ReplicationSlotSave();
+   }
 
    slot_name = NameStr(MyReplicationSlot->data.name);
    snprintf(xpos, sizeof(xpos), "%X/%X",

diff --git a/src/include/nodes/replnodes.h b/src/include/nodes/replnodes.h
index cac641985080643bf88e8e3190a40e57f2f72030..4e35be6a2868a9c21fd4e04551936f1ab5730db6 100644 (file)
--- a/src/include/nodes/replnodes.h
+++ b/src/include/nodes/replnodes.h
@@ -55,6 +55,7 @@ typedef struct CreateReplicationSlotCmd
    char       *slotname;
    ReplicationKind kind;
    char       *plugin;
+   bool        reserve_wal;
 } CreateReplicationSlotCmd;