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Commit77200c5

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Restore the portal-level snapshot for simple expressions, too.
Commits84f5c29 et al missed the need to cover plpgsql's "simpleexpression" code path. If the first thing we execute after aCOMMIT/ROLLBACK is one of those, rather than a full-fledged SPI command,we must explicitly do EnsurePortalSnapshotExists() to make sure we havean outer snapshot. Note that it wouldn't be good enough to just push asnapshot for the duration of the expression execution: what comes backmight be toasted, so we'd better have a snapshot protecting it.The test case demonstrating this fact cheats a bit by marking a SQLfunction immutable even though it fetches from a table. That'snothing 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
1 parentea5ae3a commit77200c5

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‎src/pl/plpgsql/src/expected/plpgsql_transaction.out

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@@ -430,6 +430,24 @@ SELECT * FROM test1;
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---+---
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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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DO LANGUAGE plpgsql $$
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declare

‎src/pl/plpgsql/src/pl_exec.c

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@@ -36,6 +36,7 @@
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#include"parser/parse_type.h"
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#include"parser/scansup.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/utility.h"
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#include"utils/array.h"
@@ -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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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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* 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

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

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@@ -354,6 +354,27 @@ $$;
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SELECT*FROM test1;
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-- detoast result of simple expression after commit
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CREATE TEMP TABLE test4(f1text);
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ALTERTABLE test4 ALTER COLUMN f1SET STORAGE EXTERNAL;-- disable compression
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INSERT INTO test4SELECT repeat('xyzzy',2000);
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-- immutable mark is a bit of a lie, but it serves to make call a simple expr
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-- that will return a still-toasted value
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CREATEFUNCTIONdata_source(iint) RETURNSTEXT LANGUAGE sql
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AS'select f1 from test4' IMMUTABLE;
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DO $$
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declare xtext;
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begin
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for iin1..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 $$;
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-- operations on composite types vs. internal transactions
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DO LANGUAGE plpgsql $$
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declare

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