diff options
Diffstat (limited to 'src/backend/optimizer/path/joinpath.c')
| -rw-r--r-- | src/backend/optimizer/path/joinpath.c | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c index e6ef0deb234..bd51e4f9724 100644 --- a/src/backend/optimizer/path/joinpath.c +++ b/src/backend/optimizer/path/joinpath.c @@ -2193,15 +2193,9 @@ hash_inner_and_outer(PlannerInfo *root, * able to properly guarantee uniqueness. Similarly, we can't handle * JOIN_FULL and JOIN_RIGHT, because they can produce false null * extended rows. Also, the resulting path must not be parameterized. - * We would be able to support JOIN_FULL and JOIN_RIGHT for Parallel - * Hash, since in that case we're back to a single hash table with a - * single set of match bits for each batch, but that will require - * figuring out a deadlock-free way to wait for the probe to finish. */ if (joinrel->consider_parallel && save_jointype != JOIN_UNIQUE_OUTER && - save_jointype != JOIN_FULL && - save_jointype != JOIN_RIGHT && outerrel->partial_pathlist != NIL && bms_is_empty(joinrel->lateral_relids)) { @@ -2235,9 +2229,13 @@ hash_inner_and_outer(PlannerInfo *root, * total inner path will also be parallel-safe, but if not, we'll * have to search for the cheapest safe, unparameterized inner * path. If doing JOIN_UNIQUE_INNER, we can't use any alternative - * inner path. + * inner path. If full or right join, we can't use parallelism + * (building the hash table in each backend) because no one + * process has all the match bits. */ - if (cheapest_total_inner->parallel_safe) + if (save_jointype == JOIN_FULL || save_jointype == JOIN_RIGHT) + cheapest_safe_inner = NULL; + else if (cheapest_total_inner->parallel_safe) cheapest_safe_inner = cheapest_total_inner; else if (save_jointype != JOIN_UNIQUE_INNER) cheapest_safe_inner = |