morningman commented on a change in pull request #3148: improve performent of
hash join in some case
URL: https://github.com/apache/incubator-doris/pull/3148#discussion_r395001565
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File path: be/src/exec/hash_join_node_ir.cpp
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@@ -137,11 +137,20 @@ int HashJoinNode::process_probe_batch(RowBatch*
out_batch, RowBatch* probe_batch
return rows_returned;
}
+// when build table has too many duplicated rows, the collisions will be very
serious,
+// so in some case will don't need to store duplicated value in hash table, we
can build an unique one
void HashJoinNode::process_build_batch(RowBatch* build_batch) {
// insert build row into our hash table
for (int i = 0; i < build_batch->num_rows(); ++i) {
- _hash_tbl->insert(build_batch->get_row(i));
+ if (_join_op == TJoinOp::LEFT_ANTI_JOIN|| _join_op ==
TJoinOp::RIGHT_ANTI_JOIN
Review comment:
I think these compare can be done just once when initializing the
HashJoinNode, no need to judge it for every row.
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