diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/utils/sort/tuplesort.c | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c index 10e89e52087..e8da988a73c 100644 --- a/src/backend/utils/sort/tuplesort.c +++ b/src/backend/utils/sort/tuplesort.c @@ -436,7 +436,11 @@ struct Tuplesortstate /* * This variable is shared by the single-key MinimalTuple case and the - * Datum case (which both use qsort_ssup()). Otherwise it's NULL. + * Datum case (which both use qsort_ssup()). Otherwise, it's NULL. The + * presence of a value in this field is also checked by various sort + * specialization functions as an optimization when comparing the leading + * key in a tiebreak situation to determine if there are any subsequent + * keys to sort on. */ SortSupport onlyKey; @@ -701,6 +705,13 @@ qsort_tuple_unsigned_compare(SortTuple *a, SortTuple *b, Tuplesortstate *state) if (compare != 0) return compare; + /* + * No need to waste effort calling the tiebreak function when there are + * no other keys to sort on. + */ + if (state->onlyKey != NULL) + return 0; + return state->comparetup(a, b, state); } @@ -713,9 +724,17 @@ qsort_tuple_signed_compare(SortTuple *a, SortTuple *b, Tuplesortstate *state) compare = ApplySignedSortComparator(a->datum1, a->isnull1, b->datum1, b->isnull1, &state->sortKeys[0]); + if (compare != 0) return compare; + /* + * No need to waste effort calling the tiebreak function when there are + * no other keys to sort on. + */ + if (state->onlyKey != NULL) + return 0; + return state->comparetup(a, b, state); } @@ -728,9 +747,17 @@ qsort_tuple_int32_compare(SortTuple *a, SortTuple *b, Tuplesortstate *state) compare = ApplyInt32SortComparator(a->datum1, a->isnull1, b->datum1, b->isnull1, &state->sortKeys[0]); + if (compare != 0) return compare; + /* + * No need to waste effort calling the tiebreak function when there are + * no other keys to sort on. + */ + if (state->onlyKey != NULL) + return 0; + return state->comparetup(a, b, state); } |