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Restore the portal-level snapshot for simple expressions, too.
Commits 84f5c2908
et al missed the need to cover plpgsql's "simple
expression" code path. If the first thing we execute after a
COMMIT/ROLLBACK is one of those, rather than a full-fledged SPI command,
we must explicitly do EnsurePortalSnapshotExists() to make sure we have
an outer snapshot. Note that it wouldn't be good enough to just push a
snapshot for the duration of the expression execution: what comes back
might be toasted, so we'd better have a snapshot protecting it.
The test case demonstrating this fact cheats a bit by marking a SQL
function immutable even though it fetches from a table. That's
nothing that users haven't been seen to do, though.
Per report from Jim Nasby. Back-patch to v11, like the previous fix.
Discussion: https://postgr.es/m/378885e4-f85f-fc28-6c91-c4d1c080bf26@amazon.com
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@ -430,6 +430,24 @@ SELECT * FROM test1;
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---+---
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---+---
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(0 rows)
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(0 rows)
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-- detoast result of simple expression after commit
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CREATE TEMP TABLE test4(f1 text);
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ALTER TABLE test4 ALTER COLUMN f1 SET STORAGE EXTERNAL; -- disable compression
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INSERT INTO test4 SELECT repeat('xyzzy', 2000);
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-- immutable mark is a bit of a lie, but it serves to make call a simple expr
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-- that will return a still-toasted value
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CREATE FUNCTION data_source(i int) RETURNS TEXT LANGUAGE sql
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AS 'select f1 from test4' IMMUTABLE;
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DO $$
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declare x text;
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begin
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for i in 1..3 loop
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x := data_source(i);
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commit;
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end loop;
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raise notice 'length(x) = %', length(x);
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end $$;
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NOTICE: length(x) = 10000
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-- operations on composite types vs. internal transactions
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-- operations on composite types vs. internal transactions
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DO LANGUAGE plpgsql $$
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DO LANGUAGE plpgsql $$
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declare
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declare
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@ -36,6 +36,7 @@
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#include "parser/parse_type.h"
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#include "parser/parse_type.h"
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#include "parser/scansup.h"
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#include "parser/scansup.h"
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#include "storage/proc.h"
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#include "storage/proc.h"
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#include "tcop/pquery.h"
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#include "tcop/tcopprot.h"
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#include "tcop/tcopprot.h"
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#include "tcop/utility.h"
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#include "tcop/utility.h"
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#include "utils/array.h"
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#include "utils/array.h"
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@ -6123,6 +6124,15 @@ exec_eval_simple_expr(PLpgSQL_execstate *estate,
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if (expr->expr_simple_in_use && expr->expr_simple_lxid == curlxid)
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if (expr->expr_simple_in_use && expr->expr_simple_lxid == curlxid)
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return false;
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return false;
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/*
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* Ensure that there's a portal-level snapshot, in case this simple
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* expression is the first thing evaluated after a COMMIT or ROLLBACK.
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* We'd have to do this anyway before executing the expression, so we
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* might as well do it now to ensure that any possible replanning doesn't
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* need to take a new snapshot.
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*/
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EnsurePortalSnapshotExists();
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/*
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/*
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* Revalidate cached plan, so that we will notice if it became stale. (We
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* Revalidate cached plan, so that we will notice if it became stale. (We
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* need to hold a refcount while using the plan, anyway.) If replanning
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* need to hold a refcount while using the plan, anyway.) If replanning
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@ -354,6 +354,27 @@ $$;
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SELECT * FROM test1;
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SELECT * FROM test1;
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-- detoast result of simple expression after commit
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CREATE TEMP TABLE test4(f1 text);
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ALTER TABLE test4 ALTER COLUMN f1 SET STORAGE EXTERNAL; -- disable compression
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INSERT INTO test4 SELECT repeat('xyzzy', 2000);
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-- immutable mark is a bit of a lie, but it serves to make call a simple expr
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-- that will return a still-toasted value
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CREATE FUNCTION data_source(i int) RETURNS TEXT LANGUAGE sql
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AS 'select f1 from test4' IMMUTABLE;
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DO $$
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declare x text;
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begin
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for i in 1..3 loop
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x := data_source(i);
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commit;
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end loop;
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raise notice 'length(x) = %', length(x);
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end $$;
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-- operations on composite types vs. internal transactions
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-- operations on composite types vs. internal transactions
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DO LANGUAGE plpgsql $$
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DO LANGUAGE plpgsql $$
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declare
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declare
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