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PL/pgSQL: Add support for SET TRANSACTION
A normal SQL command run inside PL/pgSQL acquires a snapshot, but SET TRANSACTION does not work anymore if a snapshot is set. So we have to handle this separately. Reviewed-by: Alexander Korotkov <a.korotkov@postgrespro.ru> Reviewed-by: Tomas Vondra <tomas.vondra@2ndquadrant.com>
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‎src/pl/plpgsql/src/expected/plpgsql_transaction.out

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -389,6 +389,35 @@ SELECT * FROM test3;
389389
1
390390
(1 row)
391391

392+
-- SET TRANSACTION
393+
DO LANGUAGE plpgsql $$
394+
BEGIN
395+
PERFORM 1;
396+
RAISE INFO '%', current_setting('transaction_isolation');
397+
COMMIT;
398+
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
399+
PERFORM 1;
400+
RAISE INFO '%', current_setting('transaction_isolation');
401+
COMMIT;
402+
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
403+
RESET TRANSACTION ISOLATION LEVEL;
404+
PERFORM 1;
405+
RAISE INFO '%', current_setting('transaction_isolation');
406+
COMMIT;
407+
END;
408+
$$;
409+
INFO: read committed
410+
INFO: repeatable read
411+
INFO: read committed
412+
-- error case
413+
DO LANGUAGE plpgsql $$
414+
BEGIN
415+
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
416+
END;
417+
$$;
418+
ERROR: SET TRANSACTION ISOLATION LEVEL must be called before any query
419+
CONTEXT: SQL statement "SET TRANSACTION ISOLATION LEVEL REPEATABLE READ"
420+
PL/pgSQL function inline_code_block line 3 at SET
392421
DROP TABLE test1;
393422
DROP TABLE test2;
394423
DROP TABLE test3;

‎src/pl/plpgsql/src/pl_exec.c

Lines changed: 35 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -305,6 +305,8 @@ static int exec_stmt_commit(PLpgSQL_execstate *estate,
305305
PLpgSQL_stmt_commit *stmt);
306306
static int exec_stmt_rollback(PLpgSQL_execstate *estate,
307307
PLpgSQL_stmt_rollback *stmt);
308+
static int exec_stmt_set(PLpgSQL_execstate *estate,
309+
PLpgSQL_stmt_set *stmt);
308310

309311
static void plpgsql_estate_setup(PLpgSQL_execstate *estate,
310312
PLpgSQL_function *func,
@@ -2005,6 +2007,10 @@ exec_stmt(PLpgSQL_execstate *estate, PLpgSQL_stmt *stmt)
20052007
rc = exec_stmt_rollback(estate, (PLpgSQL_stmt_rollback *) stmt);
20062008
break;
20072009

2010+
case PLPGSQL_STMT_SET:
2011+
rc = exec_stmt_set(estate, (PLpgSQL_stmt_set *) stmt);
2012+
break;
2013+
20082014
default:
20092015
estate->err_stmt = save_estmt;
20102016
elog(ERROR, "unrecognized cmd_type: %d", stmt->cmd_type);
@@ -4732,6 +4738,35 @@ exec_stmt_rollback(PLpgSQL_execstate *estate, PLpgSQL_stmt_rollback *stmt)
47324738
return PLPGSQL_RC_OK;
47334739
}
47344740

4741+
/*
4742+
* exec_stmt_set
4743+
*
4744+
* Execute SET/RESET statement.
4745+
*
4746+
* We just parse and execute the statement normally, but we have to do it
4747+
* without setting a snapshot, for things like SET TRANSACTION.
4748+
*/
4749+
static int
4750+
exec_stmt_set(PLpgSQL_execstate *estate, PLpgSQL_stmt_set *stmt)
4751+
{
4752+
PLpgSQL_expr *expr = stmt->expr;
4753+
int rc;
4754+
4755+
if (expr->plan == NULL)
4756+
{
4757+
exec_prepare_plan(estate, expr, 0, true);
4758+
expr->plan->no_snapshots = true;
4759+
}
4760+
4761+
rc = SPI_execute_plan(expr->plan, NULL, NULL, estate->readonly_func, 0);
4762+
4763+
if (rc != SPI_OK_UTILITY)
4764+
elog(ERROR, "SPI_execute_plan failed executing query \"%s\": %s",
4765+
expr->query, SPI_result_code_string(rc));
4766+
4767+
return PLPGSQL_RC_OK;
4768+
}
4769+
47354770
/* ----------
47364771
* exec_assign_expr Put an expression's result into a variable.
47374772
* ----------

‎src/pl/plpgsql/src/pl_funcs.c

Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -290,6 +290,8 @@ plpgsql_stmt_typename(PLpgSQL_stmt *stmt)
290290
return "COMMIT";
291291
case PLPGSQL_STMT_ROLLBACK:
292292
return "ROLLBACK";
293+
case PLPGSQL_STMT_SET:
294+
return "SET";
293295
}
294296

295297
return "unknown";
@@ -372,6 +374,7 @@ static void free_perform(PLpgSQL_stmt_perform *stmt);
372374
static void free_call(PLpgSQL_stmt_call *stmt);
373375
static void free_commit(PLpgSQL_stmt_commit *stmt);
374376
static void free_rollback(PLpgSQL_stmt_rollback *stmt);
377+
static void free_set(PLpgSQL_stmt_set *stmt);
375378
static void free_expr(PLpgSQL_expr *expr);
376379

377380

@@ -461,6 +464,9 @@ free_stmt(PLpgSQL_stmt *stmt)
461464
case PLPGSQL_STMT_ROLLBACK:
462465
free_rollback((PLpgSQL_stmt_rollback *) stmt);
463466
break;
467+
case PLPGSQL_STMT_SET:
468+
free_set((PLpgSQL_stmt_set *) stmt);
469+
break;
464470
default:
465471
elog(ERROR, "unrecognized cmd_type: %d", stmt->cmd_type);
466472
break;
@@ -624,6 +630,12 @@ free_rollback(PLpgSQL_stmt_rollback *stmt)
624630
{
625631
}
626632

633+
static void
634+
free_set(PLpgSQL_stmt_set *stmt)
635+
{
636+
free_expr(stmt->expr);
637+
}
638+
627639
static void
628640
free_exit(PLpgSQL_stmt_exit *stmt)
629641
{
@@ -820,6 +832,7 @@ static void dump_perform(PLpgSQL_stmt_perform *stmt);
820832
static void dump_call(PLpgSQL_stmt_call *stmt);
821833
static void dump_commit(PLpgSQL_stmt_commit *stmt);
822834
static void dump_rollback(PLpgSQL_stmt_rollback *stmt);
835+
static void dump_set(PLpgSQL_stmt_set *stmt);
823836
static void dump_expr(PLpgSQL_expr *expr);
824837

825838

@@ -919,6 +932,9 @@ dump_stmt(PLpgSQL_stmt *stmt)
919932
case PLPGSQL_STMT_ROLLBACK:
920933
dump_rollback((PLpgSQL_stmt_rollback *) stmt);
921934
break;
935+
case PLPGSQL_STMT_SET:
936+
dump_set((PLpgSQL_stmt_set *) stmt);
937+
break;
922938
default:
923939
elog(ERROR, "unrecognized cmd_type: %d", stmt->cmd_type);
924940
break;
@@ -1314,6 +1330,13 @@ dump_rollback(PLpgSQL_stmt_rollback *stmt)
13141330
printf("ROLLBACK\n");
13151331
}
13161332

1333+
static void
1334+
dump_set(PLpgSQL_stmt_set *stmt)
1335+
{
1336+
dump_ind();
1337+
printf("%s\n", stmt->expr->query);
1338+
}
1339+
13171340
static void
13181341
dump_exit(PLpgSQL_stmt_exit *stmt)
13191342
{

‎src/pl/plpgsql/src/pl_gram.y

Lines changed: 31 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -199,7 +199,7 @@ static void check_raise_parameters(PLpgSQL_stmt_raise *stmt);
199199
%type <stmt> stmt_return stmt_raise stmt_assert stmt_execsql
200200
%type <stmt> stmt_dynexecute stmt_for stmt_perform stmt_call stmt_getdiag
201201
%type <stmt> stmt_open stmt_fetch stmt_move stmt_close stmt_null
202-
%type <stmt> stmt_commit stmt_rollback
202+
%type <stmt> stmt_commit stmt_rollback stmt_set
203203
%type <stmt> stmt_case stmt_foreach_a
204204

205205
%type <list> proc_exceptions
@@ -327,6 +327,7 @@ static void check_raise_parameters(PLpgSQL_stmt_raise *stmt);
327327
%token <keyword> K_QUERY
328328
%token <keyword> K_RAISE
329329
%token <keyword> K_RELATIVE
330+
%token <keyword> K_RESET
330331
%token <keyword> K_RESULT_OID
331332
%token <keyword> K_RETURN
332333
%token <keyword> K_RETURNED_SQLSTATE
@@ -337,6 +338,7 @@ static void check_raise_parameters(PLpgSQL_stmt_raise *stmt);
337338
%token <keyword> K_SCHEMA
338339
%token <keyword> K_SCHEMA_NAME
339340
%token <keyword> K_SCROLL
341+
%token <keyword> K_SET
340342
%token <keyword> K_SLICE
341343
%token <keyword> K_SQLSTATE
342344
%token <keyword> K_STACKED
@@ -893,6 +895,8 @@ proc_stmt : pl_block ';'
893895
{ $$ = $1; }
894896
| stmt_rollback
895897
{ $$ = $1; }
898+
| stmt_set
899+
{ $$ = $1; }
896900
;
897901

898902
stmt_perform : K_PERFORM expr_until_semi
@@ -2206,6 +2210,30 @@ stmt_rollback : K_ROLLBACK ';'
22062210
}
22072211
;
22082212

2213+
stmt_set : K_SET
2214+
{
2215+
PLpgSQL_stmt_set *new;
2216+
2217+
new = palloc0(sizeof(PLpgSQL_stmt_set));
2218+
new->cmd_type = PLPGSQL_STMT_SET;
2219+
new->lineno = plpgsql_location_to_lineno(@1);
2220+
new->expr = read_sql_stmt("SET ");
2221+
2222+
$$ = (PLpgSQL_stmt *)new;
2223+
}
2224+
| K_RESET
2225+
{
2226+
PLpgSQL_stmt_set *new;
2227+
2228+
new = palloc0(sizeof(PLpgSQL_stmt_set));
2229+
new->cmd_type = PLPGSQL_STMT_SET;
2230+
new->lineno = plpgsql_location_to_lineno(@1);
2231+
new->expr = read_sql_stmt("RESET ");
2232+
2233+
$$ = (PLpgSQL_stmt *)new;
2234+
}
2235+
;
2236+
22092237

22102238
cursor_variable : T_DATUM
22112239
{
@@ -2494,6 +2522,7 @@ unreserved_keyword :
24942522
| K_QUERY
24952523
| K_RAISE
24962524
| K_RELATIVE
2525+
| K_RESET
24972526
| K_RESULT_OID
24982527
| K_RETURN
24992528
| K_RETURNED_SQLSTATE
@@ -2504,6 +2533,7 @@ unreserved_keyword :
25042533
| K_SCHEMA
25052534
| K_SCHEMA_NAME
25062535
| K_SCROLL
2536+
| K_SET
25072537
| K_SLICE
25082538
| K_SQLSTATE
25092539
| K_STACKED

‎src/pl/plpgsql/src/pl_scanner.c

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -158,6 +158,7 @@ static const ScanKeyword unreserved_keywords[] = {
158158
PG_KEYWORD("query", K_QUERY, UNRESERVED_KEYWORD)
159159
PG_KEYWORD("raise", K_RAISE, UNRESERVED_KEYWORD)
160160
PG_KEYWORD("relative", K_RELATIVE, UNRESERVED_KEYWORD)
161+
PG_KEYWORD("reset", K_RESET, UNRESERVED_KEYWORD)
161162
PG_KEYWORD("result_oid", K_RESULT_OID, UNRESERVED_KEYWORD)
162163
PG_KEYWORD("return", K_RETURN, UNRESERVED_KEYWORD)
163164
PG_KEYWORD("returned_sqlstate", K_RETURNED_SQLSTATE, UNRESERVED_KEYWORD)
@@ -168,6 +169,7 @@ static const ScanKeyword unreserved_keywords[] = {
168169
PG_KEYWORD("schema", K_SCHEMA, UNRESERVED_KEYWORD)
169170
PG_KEYWORD("schema_name", K_SCHEMA_NAME, UNRESERVED_KEYWORD)
170171
PG_KEYWORD("scroll", K_SCROLL, UNRESERVED_KEYWORD)
172+
PG_KEYWORD("set", K_SET, UNRESERVED_KEYWORD)
171173
PG_KEYWORD("slice", K_SLICE, UNRESERVED_KEYWORD)
172174
PG_KEYWORD("sqlstate", K_SQLSTATE, UNRESERVED_KEYWORD)
173175
PG_KEYWORD("stacked", K_STACKED, UNRESERVED_KEYWORD)

‎src/pl/plpgsql/src/plpgsql.h

Lines changed: 12 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -127,7 +127,8 @@ typedef enum PLpgSQL_stmt_type
127127
PLPGSQL_STMT_PERFORM,
128128
PLPGSQL_STMT_CALL,
129129
PLPGSQL_STMT_COMMIT,
130-
PLPGSQL_STMT_ROLLBACK
130+
PLPGSQL_STMT_ROLLBACK,
131+
PLPGSQL_STMT_SET
131132
} PLpgSQL_stmt_type;
132133

133134
/*
@@ -539,6 +540,16 @@ typedef struct PLpgSQL_stmt_rollback
539540
int lineno;
540541
} PLpgSQL_stmt_rollback;
541542

543+
/*
544+
* SET statement
545+
*/
546+
typedef struct PLpgSQL_stmt_set
547+
{
548+
PLpgSQL_stmt_type cmd_type;
549+
int lineno;
550+
PLpgSQL_expr *expr;
551+
} PLpgSQL_stmt_set;
552+
542553
/*
543554
* GET DIAGNOSTICS item
544555
*/

‎src/pl/plpgsql/src/sql/plpgsql_transaction.sql

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -317,6 +317,31 @@ $$;
317317
SELECT * FROM test3;
318318

319319

320+
-- SET TRANSACTION
321+
DO LANGUAGE plpgsql $$
322+
BEGIN
323+
PERFORM 1;
324+
RAISE INFO '%', current_setting('transaction_isolation');
325+
COMMIT;
326+
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
327+
PERFORM 1;
328+
RAISE INFO '%', current_setting('transaction_isolation');
329+
COMMIT;
330+
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
331+
RESET TRANSACTION ISOLATION LEVEL;
332+
PERFORM 1;
333+
RAISE INFO '%', current_setting('transaction_isolation');
334+
COMMIT;
335+
END;
336+
$$;
337+
338+
-- error case
339+
DO LANGUAGE plpgsql $$
340+
BEGIN
341+
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
342+
END;
343+
$$;
344+
320345
DROP TABLE test1;
321346
DROP TABLE test2;
322347
DROP TABLE test3;

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