diff options
Diffstat (limited to 'src/backend/utils')
| -rw-r--r-- | src/backend/utils/sort/tuplestore.c | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/src/backend/utils/sort/tuplestore.c b/src/backend/utils/sort/tuplestore.c index 6bfeed10896..10afc4851b4 100644 --- a/src/backend/utils/sort/tuplestore.c +++ b/src/backend/utils/sort/tuplestore.c @@ -47,7 +47,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/utils/sort/tuplestore.c,v 1.46 2009/01/01 17:23:53 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/utils/sort/tuplestore.c,v 1.47 2009/03/27 18:30:21 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -871,10 +871,17 @@ tuplestore_gettuple(Tuplestorestate *state, bool forward, * * If successful, put tuple in slot and return TRUE; else, clear the slot * and return FALSE. + * + * If copy is TRUE, the slot receives a copied tuple (allocated in current + * memory context) that will stay valid regardless of future manipulations of + * the tuplestore's state. If copy is FALSE, the slot may just receive a + * pointer to a tuple held within the tuplestore. The latter is more + * efficient but the slot contents may be corrupted if additional writes to + * the tuplestore occur. (If using tuplestore_trim, see comments therein.) */ bool tuplestore_gettupleslot(Tuplestorestate *state, bool forward, - TupleTableSlot *slot) + bool copy, TupleTableSlot *slot) { MinimalTuple tuple; bool should_free; @@ -883,6 +890,11 @@ tuplestore_gettupleslot(Tuplestorestate *state, bool forward, if (tuple) { + if (copy && !should_free) + { + tuple = heap_copy_minimal_tuple(tuple); + should_free = true; + } ExecStoreMinimalTuple(tuple, slot, should_free); return true; } @@ -1107,7 +1119,10 @@ tuplestore_trim(Tuplestorestate *state) * since tuplestore_gettuple returns a direct pointer to our * internal copy of the tuple, it's likely that the caller has * still got the tuple just before "current" referenced in a slot. - * So we keep one extra tuple before the oldest "current". + * So we keep one extra tuple before the oldest "current". (Strictly + * speaking, we could require such callers to use the "copy" flag to + * tuplestore_gettupleslot, but for efficiency we allow this one case + * to not use "copy".) */ nremove = oldest - 1; if (nremove <= 0) |