spi_printtup() has the following code (spi.c:1798):
if (tuptable->free == 0)
{
tuptable->free = 256;
tuptable->alloced += tuptable->free;
tuptable->vals = (HeapTuple *) repalloc(tuptable->vals,
tuptable->alloced * sizeof(HeapTuple));
}
i.e., it grows the size of the tuptable by a fixed amount when it runs
out of space. That seems odd; doubling the size of the table would be
more standard. Does anyone know if there is a rationale for this
behavior?
Attached is a one-liner to double the size of the table when space is
exhausted. Constructing a simple test case in which a large result is
materialized via SPI_execute() (e.g., by passing two large queries to
crosstab() from contrib/tablefunc), this change reduces the time
required to exceed the palloc size limit from ~300 seconds to ~93
seconds on my laptop.
Of course, using SPI_execute() rather than cursors for queries with
large result sets is not a great idea, but there is demonstrably code
that does this (e.g., contrib/tablefunc -- I'll send a patch for that
shortly).
Neil
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index d544ad9..2573b3f 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -1797,7 +1797,7 @@ spi_printtup(TupleTableSlot *slot, DestReceiver *self)
if (tuptable->free == 0)
{
- tuptable->free = 256;
+ tuptable->free = tuptable->alloced;
tuptable->alloced += tuptable->free;
tuptable->vals = (HeapTuple *) repalloc(tuptable->vals,
tuptable->alloced * sizeof(HeapTuple));
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
