Add facility to copy replication slots

This allows the user to create duplicates of existing replication slots,
either logical or physical, and even changing properties such as whether
they are temporary or the output plugin used.

There are multiple uses for this, such as initializing multiple replicas
using the slot for one base backup; when doing investigation of logical
replication issues; and to select a different output plugins.

Author: Masahiko Sawada
Reviewed-by: Michael Paquier, Andres Freund, Petr Jelinek
Discussion: https://postgr.es/m/CAD21AoAm7XX8y_tOPP6j4Nzzch12FvA1wPqiO690RCk+uYVstg@mail.gmail.com

3 files changed, 37 insertions, 1 deletions

diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 1fe54c26653..bfd2bfc186c 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201904031
+#define CATALOG_VERSION_NO	201904051
 
 #endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index fb257c17c89..ad4519e0011 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -9774,6 +9774,20 @@
   proargmodes => '{i,i,i,o,o}',
   proargnames => '{slot_name,immediately_reserve,temporary,slot_name,lsn}',
   prosrc => 'pg_create_physical_replication_slot' },
+{ oid => '4220', descr => 'copy a physical replication slot, changing temporality',
+  proname => 'pg_copy_physical_replication_slot', provolatile => 'v',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool',
+  proallargtypes => '{name,name,bool,name,pg_lsn}',
+  proargmodes => '{i,i,i,o,o}',
+  proargnames => '{src_slot_name,dst_slot_name,temporary,slot_name,lsn}',
+  prosrc => 'pg_copy_physical_replication_slot_a' },
+{ oid => '4221', descr => 'copy a physical replication slot',
+  proname => 'pg_copy_physical_replication_slot', provolatile => 'v',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name',
+  proallargtypes => '{name,name,name,pg_lsn}',
+  proargmodes => '{i,i,o,o}',
+  proargnames => '{src_slot_name,dst_slot_name,slot_name,lsn}',
+  prosrc => 'pg_copy_physical_replication_slot_b' },
 { oid => '3780', descr => 'drop a replication slot',
   proname => 'pg_drop_replication_slot', provolatile => 'v', proparallel => 'u',
   prorettype => 'void', proargtypes => 'name',
@@ -9794,6 +9808,27 @@
   proargmodes => '{i,i,i,o,o}',
   proargnames => '{slot_name,plugin,temporary,slot_name,lsn}',
   prosrc => 'pg_create_logical_replication_slot' },
+{ oid => '4222', descr => 'copy a logical replication slot, changing temporality and plugin',
+  proname => 'pg_copy_logical_replication_slot', provolatile => 'v',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool name',
+  proallargtypes => '{name,name,bool,name,name,pg_lsn}',
+  proargmodes => '{i,i,i,i,o,o}',
+  proargnames => '{src_slot_name,dst_slot_name,temporary,plugin,slot_name,lsn}',
+  prosrc => 'pg_copy_logical_replication_slot_a' },
+{ oid => '4223', descr => 'copy a logical replication slot, changing temporality',
+  proname => 'pg_copy_logical_replication_slot', provolatile => 'v',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name bool',
+  proallargtypes => '{name,name,bool,name,pg_lsn}',
+  proargmodes => '{i,i,i,o,o}',
+  proargnames => '{src_slot_name,dst_slot_name,temporary,slot_name,lsn}',
+  prosrc => 'pg_copy_logical_replication_slot_b' },
+{ oid => '4224', descr => 'copy a logical replication slot',
+  proname => 'pg_copy_logical_replication_slot', provolatile => 'v',
+  proparallel => 'u', prorettype => 'record', proargtypes => 'name name',
+  proallargtypes => '{name,name,name,pg_lsn}',
+  proargmodes => '{i,i,o,o}',
+  proargnames => '{src_slot_name,dst_slot_name,slot_name,lsn}',
+  prosrc => 'pg_copy_logical_replication_slot_c' },
 { oid => '3782', descr => 'get changes from replication slot',
   proname => 'pg_logical_slot_get_changes', procost => '1000',
   prorows => '1000', provariadic => 'text', proisstrict => 'f',
diff --git a/src/include/replication/logical.h b/src/include/replication/logical.h
index c8ffc4c4347..0a2a63a48c8 100644
--- a/src/include/replication/logical.h
+++ b/src/include/replication/logical.h
@@ -97,6 +97,7 @@ extern void CheckLogicalDecodingRequirements(void);
 extern LogicalDecodingContext *CreateInitDecodingContext(char *plugin,
 						  List *output_plugin_options,
 						  bool need_full_snapshot,
+						  XLogRecPtr restart_lsn,
 						  XLogPageReadCB read_page,
 						  LogicalOutputPluginWriterPrepareWrite prepare_write,
 						  LogicalOutputPluginWriterWrite do_write,