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Commit0da3a9b

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Fix failure to consider failure cases in GetComboCommandId().
Failure to initially palloc the comboCids array, or to realloc it biggerwhen needed, left combocid's data structures in an inconsistent state thatwould cause trouble if the top transaction continues to execute. Notedwhile examining a user complaint about the amount of memory used for this.(There's not much we can do about that, but it does point up that repallocfailure has a non-negligible chance of occurring here.)In HEAD/9.5, also avoid possible invocation of memcpy() with a null pointerin SerializeComboCIDState; cf commit13bba02.
1 parentc5ef8ce commit0da3a9b

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1 file changed

+23
-20
lines changed

1 file changed

+23
-20
lines changed

‎src/backend/utils/time/combocid.c

Lines changed: 23 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -217,6 +217,13 @@ GetComboCommandId(CommandId cmin, CommandId cmax)
217217
{
218218
HASHCTLhash_ctl;
219219

220+
/* Make array first; existence of hash table asserts array exists */
221+
comboCids= (ComboCidKeyData*)
222+
MemoryContextAlloc(TopTransactionContext,
223+
sizeof(ComboCidKeyData)*CCID_ARRAY_SIZE);
224+
sizeComboCids=CCID_ARRAY_SIZE;
225+
usedComboCids=0;
226+
220227
memset(&hash_ctl,0,sizeof(hash_ctl));
221228
hash_ctl.keysize=sizeof(ComboCidKeyData);
222229
hash_ctl.entrysize=sizeof(ComboCidEntryData);
@@ -226,12 +233,20 @@ GetComboCommandId(CommandId cmin, CommandId cmax)
226233
CCID_HASH_SIZE,
227234
&hash_ctl,
228235
HASH_ELEM |HASH_BLOBS |HASH_CONTEXT);
236+
}
237+
238+
/*
239+
* Grow the array if there's not at least one free slot. We must do this
240+
* before possibly entering a new hashtable entry, else failure to
241+
* repalloc would leave a corrupt hashtable entry behind.
242+
*/
243+
if (usedComboCids >=sizeComboCids)
244+
{
245+
intnewsize=sizeComboCids*2;
229246

230247
comboCids= (ComboCidKeyData*)
231-
MemoryContextAlloc(TopTransactionContext,
232-
sizeof(ComboCidKeyData)*CCID_ARRAY_SIZE);
233-
sizeComboCids=CCID_ARRAY_SIZE;
234-
usedComboCids=0;
248+
repalloc(comboCids,sizeof(ComboCidKeyData)*newsize);
249+
sizeComboCids=newsize;
235250
}
236251

237252
/* Lookup or create a hash entry with the desired cmin/cmax */
@@ -250,20 +265,7 @@ GetComboCommandId(CommandId cmin, CommandId cmax)
250265
returnentry->combocid;
251266
}
252267

253-
/*
254-
* We have to create a new combo cid. Check that there's room for it in
255-
* the array, and grow it if there isn't.
256-
*/
257-
if (usedComboCids >=sizeComboCids)
258-
{
259-
/* We need to grow the array */
260-
intnewsize=sizeComboCids*2;
261-
262-
comboCids= (ComboCidKeyData*)
263-
repalloc(comboCids,sizeof(ComboCidKeyData)*newsize);
264-
sizeComboCids=newsize;
265-
}
266-
268+
/* We have to create a new combo cid; we already made room in the array */
267269
combocid=usedComboCids;
268270

269271
comboCids[combocid].cmin=cmin;
@@ -327,8 +329,9 @@ SerializeComboCIDState(Size maxsize, char *start_address)
327329
elog(ERROR,"not enough space to serialize ComboCID state");
328330

329331
/* Now, copy the actual cmin/cmax pairs. */
330-
memcpy(start_address+sizeof(int),comboCids,
331-
(sizeof(ComboCidKeyData)*usedComboCids));
332+
if (usedComboCids>0)
333+
memcpy(start_address+sizeof(int),comboCids,
334+
(sizeof(ComboCidKeyData)*usedComboCids));
332335
}
333336

334337
/*

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