Fix thinko in safeguard for negative availMem.

Also, use pass read_buffer_size * numInputTapes rather than just availMem
to USEMEM, to be neat.

Peter Geoghegan.

diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 46eecbf942f77a11473e966416f8a62a0468de08..baf87b3cdfc9c4bb15de24305e806de828bde9d7 100644 (file)
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -2669,8 +2669,8 @@ mergeruns(Tuplesortstate *state)
             (state->availMem) / 1024, numInputTapes);
 #endif
 
-   state->read_buffer_size = Min(state->availMem / numInputTapes, 0);
-   USEMEM(state, state->availMem);
+   state->read_buffer_size = Max(state->availMem / numInputTapes, 0);
+   USEMEM(state, state->read_buffer_size * numInputTapes);
 
    /* End of step D2: rewind all output tapes to prepare for merging */
    for (tapenum = 0; tapenum < state->tapeRange; tapenum++)