ArrayBuildState, per trouble report from Merlin Moncure. By adopting
this fix, we are essentially deciding that aggregate final-functions
should not modify their inputs ever. Adjust documentation and comments
to match that conclusion.
index b223888f9ed92c70475b1f3499ea4fd555433dc9..1175b3640d70977fcc892c0737ae39bcd0c35473 100644 (file)
-<!-- $PostgreSQL: pgsql/doc/src/sgml/xaggr.sgml,v 1.37 2008年12月28日 18:53:54 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/xaggr.sgml,v 1.38 2009年06月20日 18:45:28 tgl Exp $ -->
<sect1 id="xaggr">
<title>User-Defined Aggregates</title>
@@ -175,10 +175,14 @@ SELECT attrelid::regclass, array_accum(atttypid::regtype)
(IsA(fcinfo->context, AggState) ||
IsA(fcinfo->context, WindowAggState)))
</programlisting>
- One reason for checking this is that when it is true, the first input
+ One reason for checking this is that when it is true for a transition
+ function, the first input
must be a temporary transition value and can therefore safely be modified
in-place rather than allocating a new copy. (This is the <emphasis>only</>
- case where it is safe for a function to modify a pass-by-reference input.)
+ case where it is safe for a function to modify a pass-by-reference input.
+ In particular, aggregate final functions should not modify their inputs in
+ any case, because in some cases they will be re-executed on the same
+ final transition value.)
See <literal>int8inc()</> for an example.
</para>
index 0d9eb21a919e5690e19e67d043087be3d982f647..7343cb3752ecec1a7246d51851bf80090230bcfb 100644 (file)
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/executor/nodeWindowAgg.c,v 1.5 2009年06月11日 14:48:57 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/executor/nodeWindowAgg.c,v 1.6 2009年06月20日 18:45:28 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -410,9 +410,8 @@ eval_windowaggregates(WindowAggState *winstate)
* need the current aggregate value. This is considerably more efficient
* than the naive approach of re-running the entire aggregate calculation
* for each current row. It does assume that the final function doesn't
- * damage the running transition value. (Some C-coded aggregates do that
- * for efficiency's sake --- but they are supposed to do so only when
- * their fcinfo->context is an AggState, not a WindowAggState.)
+ * damage the running transition value, but we have the same assumption
+ * in nodeAgg.c too (when it rescans an existing hash table).
*
* In many common cases, multiple rows share the same frame and hence the
* same aggregate value. (In particular, if there's no ORDER BY in a RANGE
index c30d6b42b07cb959247921e2ff2cd5494fe0fac3..a1f48d8784c5ddbef0e0584b8018731300d177ef 100644 (file)
* Copyright (c) 2003-2009, PostgreSQL Global Development Group
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/adt/array_userfuncs.c,v 1.30 2009年06月11日 14:49:03 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/array_userfuncs.c,v 1.31 2009年06月20日 18:45:28 tgl Exp $
*
*-------------------------------------------------------------------------
*/
dims[0] = state->nelems;
lbs[0] = 1;
- /* Release working state if regular aggregate, but not if window agg */
+ /*
+ * Make the result. We cannot release the ArrayBuildState because
+ * sometimes aggregate final functions are re-executed.
+ */
result = makeMdArrayResult(state, 1, dims, lbs,
CurrentMemoryContext,
- IsA(fcinfo->context, AggState));
+ false);
PG_RETURN_DATUM(result);
}
index b3973fbccb97379a45376d3b6735a3b294096e6b..54c489a896911668b777ab05a571e966ec1eb3bd 100644 (file)
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/adt/arrayfuncs.c,v 1.157 2009年06月11日 14:49:03 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/arrayfuncs.c,v 1.158 2009年06月20日 18:45:28 tgl Exp $
*
*-------------------------------------------------------------------------
*/
}
}
- /* Use datumCopy to ensure pass-by-ref stuff is copied into mcontext */
+ /*
+ * Ensure pass-by-ref stuff is copied into mcontext; and detoast it too
+ * if it's varlena. (You might think that detoasting is not needed here
+ * because construct_md_array can detoast the array elements later.
+ * However, we must not let construct_md_array modify the ArrayBuildState
+ * because that would mean array_agg_finalfn damages its input, which
+ * is verboten. Also, this way frequently saves one copying step.)
+ */
if (!disnull && !astate->typbyval)
- dvalue = datumCopy(dvalue, astate->typbyval, astate->typlen);
+ {
+ if (astate->typlen == -1)
+ dvalue = PointerGetDatum(PG_DETOAST_DATUM_COPY(dvalue));
+ else
+ dvalue = datumCopy(dvalue, astate->typbyval, astate->typlen);
+ }
astate->dvalues[astate->nelems] = dvalue;
astate->dnulls[astate->nelems] = disnull;