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Implement WAIT FOR command

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WAIT FOR is to be used on standby and specifies waiting for
the specific WAL location to be replayed.  This option is useful when
the user makes some data changes on primary and needs a guarantee to see
these changes are on standby.

WAIT FOR needs to wait without any snapshot held.  Otherwise, the snapshot
could prevent the replay of WAL records, implying a kind of self-deadlock.
This is why separate utility command seems appears to be the most robust
way to implement this functionality.  It's not possible to implement this as
a function.  Previous experience shows that stored procedures also have
limitation in this aspect.

Discussion: https://www.postgresql.org/message-id/flat/CAPpHfdsjtZLVzxjGT8rJHCYbM0D5dwkO+BBjcirozJ6nYbOW8Q@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/flat/CABPTF7UNft368x-RgOXkfj475OwEbp%2BVVO-wEXz7StgjD_%3D6sw%40mail.gmail.com
Author: Kartyshov Ivan <i.kartyshov@postgrespro.ru>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Xuneng Zhou <xunengzhou@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Reviewed-by: Euler Taveira <euler@eulerto.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: jian he <jian.universality@gmail.com>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com>
This commit is contained in:
Alexander Korotkov
2025-11-05 11:43:55 +02:00
parent 3b4e53a075
commit 447aae13b0
21 changed files with 931 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
src/backend/parser/gram.y
View File

@@ -308,7 +308,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
SecLabelStmt SelectStmt TransactionStmt TransactionStmtLegacy TruncateStmt
UnlistenStmt UpdateStmt VacuumStmt
VariableResetStmt VariableSetStmt VariableShowStmt
ViewStmt CheckPointStmt CreateConversionStmt
ViewStmt WaitStmt CheckPointStmt CreateConversionStmt
DeallocateStmt PrepareStmt ExecuteStmt
DropOwnedStmt ReassignOwnedStmt
AlterTSConfigurationStmt AlterTSDictionaryStmt
@@ -325,6 +325,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
%type <boolean> opt_concurrently
%type <dbehavior> opt_drop_behavior
%type <list> opt_utility_option_list
%type <list> opt_wait_with_clause
%type <list> utility_option_list
%type <defelt> utility_option_elem
%type <str> utility_option_name
@@ -678,7 +679,6 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
json_object_constructor_null_clause_opt
json_array_constructor_null_clause_opt
/*
* Non-keyword token types. These are hard-wired into the "flex" lexer.
* They must be listed first so that their numeric codes do not depend on
@@ -748,7 +748,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
LABEL LANGUAGE LARGE_P LAST_P LATERAL_P
LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED LSN_P
MAPPING MATCH MATCHED MATERIALIZED MAXVALUE MERGE MERGE_ACTION METHOD
MINUTE_P MINVALUE MODE MONTH_P MOVE
@@ -792,7 +792,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
VACUUM VALID VALIDATE VALIDATOR VALUE_P VALUES VARCHAR VARIADIC VARYING
VERBOSE VERSION_P VIEW VIEWS VIRTUAL VOLATILE
WHEN WHERE WHITESPACE_P WINDOW WITH WITHIN WITHOUT WORK WRAPPER WRITE
WAIT WHEN WHERE WHITESPACE_P WINDOW WITH WITHIN WITHOUT WORK WRAPPER WRITE
XML_P XMLATTRIBUTES XMLCONCAT XMLELEMENT XMLEXISTS XMLFOREST XMLNAMESPACES
XMLPARSE XMLPI XMLROOT XMLSERIALIZE XMLTABLE
@@ -1120,6 +1120,7 @@ stmt:
| VariableSetStmt
| VariableShowStmt
| ViewStmt
| WaitStmt
| /*EMPTY*/
{ $$ = NULL; }
;
@@ -16482,6 +16483,26 @@ xml_passing_mech:
| BY VALUE_P
;
/*****************************************************************************
*
* WAIT FOR LSN
*
*****************************************************************************/
WaitStmt:
WAIT FOR LSN_P Sconst opt_wait_with_clause
{
WaitStmt *n = makeNode(WaitStmt);
n->lsn_literal = $4;
n->options = $5;
$$ = (Node *) n;
}
;
opt_wait_with_clause:
WITH '(' utility_option_list ')' { $$ = $3; }
| /*EMPTY*/ { $$ = NIL; }
;
/*
* Aggregate decoration clauses
@@ -17969,6 +17990,7 @@ unreserved_keyword:
| LOCK_P
| LOCKED
| LOGGED
| LSN_P
| MAPPING
| MATCH
| MATCHED
@@ -18139,6 +18161,7 @@ unreserved_keyword:
| VIEWS
| VIRTUAL
| VOLATILE
| WAIT
| WHITESPACE_P
| WITHIN
| WITHOUT
@@ -18585,6 +18608,7 @@ bare_label_keyword:
| LOCK_P
| LOCKED
| LOGGED
| LSN_P
| MAPPING
| MATCH
| MATCHED
@@ -18796,6 +18820,7 @@ bare_label_keyword:
| VIEWS
| VIRTUAL
| VOLATILE
| WAIT
| WHEN
| WHITESPACE_P
| WORK