Hello,
Temporary tables are often used to store transient data in
batch processing and the contents can be accessed multiple
times. However, frequent use of temporary tables has a problem
that the system catalog tends to bloat. I know there has been
several proposals to attack this problem, but I would like to
propose a new one.
The idea is to use Ephemeral Named Relation (ENR) like a
temporary table. ENR information is not stored into the system
catalog, but in QueryEnvironment, so it never bloat the system
catalog.
Although we cannot perform insert, update or delete on ENR,
I wonder it could be beneficial if we need to reference to a
result of a query multiple times in a batch processing.
The attached is a concept patch. This adds a new syntax
"OPEN cursor INTO TABLE tablename" to pl/pgSQL, that stores
a result of the cursor query into a ENR with specified name.
However, this is a tentative interface to demonstrate the
concept of feature.
Here is an example;
postgres=# \sf fnc
CREATE OR REPLACE FUNCTION public.fnc()
RETURNS TABLE(sum1 integer, avg1 integer, sum2 integer, avg2 integer)
LANGUAGE plpgsql
AS $function$
DECLARE
sum1 integer;
sum2 integer;
avg1 integer;
avg2 integer;
curs CURSOR FOR SELECT aid, bid, abalance FROM pgbench_accounts
WHERE abalance BETWEEN 100 AND 200;
BEGIN
OPEN curs INTO TABLE tmp_accounts;
SELECT count(abalance) , avg(abalance) INTO sum1, avg1
FROM tmp_accounts;
SELECT count(bbalance), avg(bbalance) INTO sum2, avg2
FROM tmp_accounts a, pgbench_branches b WHERE a.bid = b.bid;
RETURN QUERY SELECT sum1,avg1,sum2,avg2;
END;
$function$
postgres=# select fnc();
fnc
--------------------
(541,151,541,3937)
(1 row)
As above, we can use the same query result for multiple
aggregations, and also join it with other tables.
What do you think of using ENR for this way?
Regards,
Yugo Nagata
--
Yugo NAGATA <nag...@sraoss.co.jp>
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index e3a170c38b..27e94ecc87 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -20,6 +20,7 @@
#include "access/xact.h"
#include "catalog/heap.h"
#include "catalog/pg_type.h"
+#include "commands/portalcmds.h"
#include "commands/trigger.h"
#include "executor/executor.h"
#include "executor/spi_priv.h"
@@ -3378,3 +3379,30 @@ SPI_register_trigger_data(TriggerData *tdata)
return SPI_OK_TD_REGISTER;
}
+
+int
+SPI_register_portal(Portal portal, char *name)
+{
+ int rc;
+ EphemeralNamedRelation enr;
+
+ if (portal == NULL || name == NULL)
+ return SPI_ERROR_ARGUMENT;
+
+ PortalCreateHoldStore(portal);
+ PersistHoldablePortal(portal);
+
+ enr = palloc(sizeof(EphemeralNamedRelationData));
+
+ enr->md.name = name;
+ enr->md.reliddesc = InvalidOid;
+ enr->md.tupdesc = portal->tupDesc;
+ enr->md.enrtype = ENR_NAMED_TUPLESTORE;
+ enr->md.enrtuples = tuplestore_tuple_count(portal->holdStore);
+ enr->reldata = portal->holdStore;
+ rc = SPI_register_relation(enr);
+ if (rc != SPI_OK_REL_REGISTER)
+ return rc;
+
+ return SPI_OK_TD_REGISTER;
+}
diff --git a/src/include/executor/spi.h b/src/include/executor/spi.h
index d1de139a3b..40753dc78a 100644
--- a/src/include/executor/spi.h
+++ b/src/include/executor/spi.h
@@ -199,6 +199,7 @@ extern void SPI_cursor_close(Portal portal);
extern int SPI_register_relation(EphemeralNamedRelation enr);
extern int SPI_unregister_relation(const char *name);
extern int SPI_register_trigger_data(TriggerData *tdata);
+extern int SPI_register_portal(Portal portal, char *name);
extern void SPI_start_transaction(void);
extern void SPI_commit(void);
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index b0a2cac227..5d561b39bd 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -4776,6 +4776,9 @@ exec_stmt_open(PLpgSQL_execstate *estate, PLpgSQL_stmt_open *stmt)
elog(ERROR, "could not open cursor: %s",
SPI_result_code_string(SPI_result));
+ if (stmt->tablename)
+ SPI_register_portal(portal, stmt->tablename);
+
/*
* If cursor variable was NULL, store the generated portal name in it,
* after verifying it's okay to assign to.
diff --git a/src/pl/plpgsql/src/pl_gram.y b/src/pl/plpgsql/src/pl_gram.y
index edeb72c380..576ea86943 100644
--- a/src/pl/plpgsql/src/pl_gram.y
+++ b/src/pl/plpgsql/src/pl_gram.y
@@ -185,7 +185,7 @@ static void check_raise_parameters(PLpgSQL_stmt_raise *stmt);
%type <ival> foreach_slice
%type <stmt> for_control
-%type <str> any_identifier opt_block_label opt_loop_label opt_label
+%type <str> any_identifier opt_block_label opt_into_table opt_loop_label opt_label
%type <str> option_value
%type <list> proc_sect stmt_elsifs stmt_else
@@ -2064,7 +2064,17 @@ stmt_dynexecute : K_EXECUTE
;
-stmt_open : K_OPEN cursor_variable
+opt_into_table :
+ {
+ $$ = NULL;
+ }
+ | K_INTO K_TABLE any_identifier
+ {
+ $$ = $3;
+ }
+ ;
+
+stmt_open : K_OPEN cursor_variable opt_into_table
{
PLpgSQL_stmt_open *new;
int tok;
@@ -2075,6 +2085,7 @@ stmt_open : K_OPEN cursor_variable
new->stmtid = ++plpgsql_curr_compile->nstatements;
new->curvar = $2->dno;
new->cursor_options = CURSOR_OPT_FAST_PLAN;
+ new->tablename = $3;
if ($2->cursor_explicit_expr == NULL)
{
diff --git a/src/pl/plpgsql/src/plpgsql.h b/src/pl/plpgsql/src/plpgsql.h
index 355c9f678d..f1b1fa147b 100644
--- a/src/pl/plpgsql/src/plpgsql.h
+++ b/src/pl/plpgsql/src/plpgsql.h
@@ -768,6 +768,7 @@ typedef struct PLpgSQL_stmt_open
PLpgSQL_expr *query;
PLpgSQL_expr *dynquery;
List *params; /* USING expressions */
+ char *tablename;
} PLpgSQL_stmt_open;
/*
