Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commitd0ab203

Browse files
committed
Fix order of operations in ExecEvalFieldStoreDeForm().
If the given composite datum is toasted out-of-line,DatumGetHeapTupleHeader will perform database accesses to detoast it.That can invalidate the result of get_cached_rowtype, as documented(perhaps not plainly enough) in that function's API spec; which leadsto strange errors or crashes when we try to use the TupleDesc to readthe tuple. In short then, trying to update a field of a compositecolumn could fail intermittently if the overall column value is wideenough to require toasting.We can fix the bug at no cost by just changing the order ofoperations, since we don't need the TupleDesc until after detoasting.(Other callers of get_cached_rowtype appear to get this right already,so there's only one bug.)Note that the added regression test case reveals this bug reliablyonly with debug_discard_caches/CLOBBER_CACHE_ALWAYS.Per bug #17994 from Alexander Lakhin. Sadly, this patch does not fixthe missing-values issue revealed in the bug discussion; we'll needsome more work to cover that.Discussion:https://postgr.es/m/17994-5c7100b51b4790e9@postgresql.org
1 parentf428440 commitd0ab203

File tree

3 files changed

+31
-12
lines changed

3 files changed

+31
-12
lines changed

‎src/backend/executor/execExprInterp.c

Lines changed: 17 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -1952,7 +1952,8 @@ CheckOpSlotCompatibility(ExprEvalStep *op, TupleTableSlot *slot)
19521952
* changed: if not NULL, *changed is set to true on any update
19531953
*
19541954
* The returned TupleDesc is not guaranteed pinned; caller must pin it
1955-
* to use it across any operation that might incur cache invalidation.
1955+
* to use it across any operation that might incur cache invalidation,
1956+
* including for example detoasting of input tuples.
19561957
* (The TupleDesc is always refcounted, so just use IncrTupleDescRefCount.)
19571958
*
19581959
* NOTE: because composite types can change contents, we must be prepared
@@ -3111,17 +3112,6 @@ ExecEvalFieldSelect(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
31113112
void
31123113
ExecEvalFieldStoreDeForm(ExprState*state,ExprEvalStep*op,ExprContext*econtext)
31133114
{
3114-
TupleDesctupDesc;
3115-
3116-
/* Lookup tupdesc if first time through or if type changes */
3117-
tupDesc=get_cached_rowtype(op->d.fieldstore.fstore->resulttype,-1,
3118-
op->d.fieldstore.rowcache,NULL);
3119-
3120-
/* Check that current tupdesc doesn't have more fields than we allocated */
3121-
if (unlikely(tupDesc->natts>op->d.fieldstore.ncolumns))
3122-
elog(ERROR,"too many columns in composite type %u",
3123-
op->d.fieldstore.fstore->resulttype);
3124-
31253115
if (*op->resnull)
31263116
{
31273117
/* Convert null input tuple into an all-nulls row */
@@ -3137,13 +3127,28 @@ ExecEvalFieldStoreDeForm(ExprState *state, ExprEvalStep *op, ExprContext *econte
31373127
DatumtupDatum=*op->resvalue;
31383128
HeapTupleHeadertuphdr;
31393129
HeapTupleDatatmptup;
3130+
TupleDesctupDesc;
31403131

31413132
tuphdr=DatumGetHeapTupleHeader(tupDatum);
31423133
tmptup.t_len=HeapTupleHeaderGetDatumLength(tuphdr);
31433134
ItemPointerSetInvalid(&(tmptup.t_self));
31443135
tmptup.t_tableOid=InvalidOid;
31453136
tmptup.t_data=tuphdr;
31463137

3138+
/*
3139+
* Lookup tupdesc if first time through or if type changes. Because
3140+
* we don't pin the tupdesc, we must not do this lookup until after
3141+
* doing DatumGetHeapTupleHeader: that could do database access while
3142+
* detoasting the datum.
3143+
*/
3144+
tupDesc=get_cached_rowtype(op->d.fieldstore.fstore->resulttype,-1,
3145+
op->d.fieldstore.rowcache,NULL);
3146+
3147+
/* Check that current tupdesc doesn't have more fields than allocated */
3148+
if (unlikely(tupDesc->natts>op->d.fieldstore.ncolumns))
3149+
elog(ERROR,"too many columns in composite type %u",
3150+
op->d.fieldstore.fstore->resulttype);
3151+
31473152
heap_deform_tuple(&tmptup,tupDesc,
31483153
op->d.fieldstore.values,
31493154
op->d.fieldstore.nulls);

‎src/test/regress/expected/rowtypes.out

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -139,6 +139,15 @@ select (fn).first, substr((fn).last, 1, 20), length((fn).last) from people;
139139
Jim | abcdefghijklabcdefgh | 1200000
140140
(2 rows)
141141

142+
-- try an update on a toasted composite value, too
143+
update people set fn.first = 'Jack';
144+
select (fn).first, substr((fn).last, 1, 20), length((fn).last) from people;
145+
first | substr | length
146+
-------+----------------------+---------
147+
Jack | Blow | 4
148+
Jack | abcdefghijklabcdefgh | 1200000
149+
(2 rows)
150+
142151
-- Test row comparison semantics. Prior to PG 8.2 we did this in a totally
143152
-- non-spec-compliant way.
144153
select ROW(1,2) < ROW(1,3) as true;

‎src/test/regress/sql/rowtypes.sql

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -76,6 +76,11 @@ insert into people select ('Jim', f1, null)::fullname, current_date from pp;
7676

7777
select (fn).first, substr((fn).last,1,20), length((fn).last)from people;
7878

79+
-- try an update on a toasted composite value, too
80+
update peoplesetfn.first='Jack';
81+
82+
select (fn).first, substr((fn).last,1,20), length((fn).last)from people;
83+
7984
-- Test row comparison semantics. Prior to PG 8.2 we did this in a totally
8085
-- non-spec-compliant way.
8186

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp