On Fri, Aug 14, 2015 at 4:54 PM, Andres Freund <[email protected]> wrote:
> On 2015-08-14 16:44:44 +0900, Michael Paquier wrote:
>> Commit 6fcd8851, which is the result of this thread, is not touching
>> the replication protocol at all. This looks like an oversight to me:
>> we should be a maximum consistent between the SQL interface and the
>> replication protocol if possible, and it looks useful to me to be able
>> to set restart_lsn when creating the slot as well when using a
>> replication connection.
>
> It wasn't, at least not from my side. You can relatively easily do
> nearly the same just by connecting to the slot and sending a feedback
> message. The complaint upthread (and/or a related thread) was that it's
> not possible to do the same from SQL.
>
> It'd be a good additional to offer the same facility to the replication
> protocol.
> [...]
> I'd name it RESERVE_WAL. My feeling is that the options for the logical
> case are geared towards the output plugin, not the walsender. I think
> it'd be confusing to use (slot_options) differently for physical slots.
Well, this has taken less time than I thought:
=# CREATE_REPLICATION_SLOT toto PHYSICAL;
slot_name | consistent_point | snapshot_name | output_plugin
-----------+------------------+---------------+---------------
toto | 0/0 | null | null
(1 row)
=# CREATE_REPLICATION_SLOT toto2 PHYSICAL RESERVE_WAL;
slot_name | consistent_point | snapshot_name | output_plugin
-----------+------------------+---------------+---------------
toto2 | 0/0 | null | null
(1 row)
=# \q
$ psql -c 'select slot_name,restart_lsn from pg_replication_slots'
slot_name | restart_lsn
-----------+-------------
toto |
toto2 | 0/1738850
(2 rows)
What do you want to do with that? Do you wish to have a look at it or
should I register it in the next CF? I am fine with both, though this
is tightly linked with the feature already committed.
Regards,
--
Michael
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 42e9497..df49fa3 100644
--- 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 the <acronym>LSN</> for this physical replication
+ slot is reserved immediately; otherwise the <acronym>LSN</> is
+ reserved on first 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 e9177ca..077d67d 100644
--- 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;
$$ = (Node *) cmd;
}
/* CREATE_REPLICATION_SLOT slot LOGICAL plugin */
@@ -268,6 +271,12 @@ opt_physical:
| /* EMPTY */
;
+opt_reserve_wal:
+ K_RESERVE_WAL
+ { $$ = 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 056cc14..d7030c1 100644
--- 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 e1bab07..9142811 100644
--- 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 cac6419..4e35be6 100644
--- 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;
--
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