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Add support for hash join on rowid #203
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ienkovich
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Feb 22, 2023
| executor_->cgen_state_->castToTypeIn(key_lvs.front(), 64)}; | ||
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| const auto& query_info = getInnerQueryInfo(val_col_var).info; | ||
| if (query_info.getPhysicalNumTuples() == 0) { |
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Just curious why we can't always use rhs_source_col_range_. In theory, for an empty table, we should have some invalid ranges for all columns where max < min.
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Looks like it's set for rowid specially -- I wonder if that's worth changing? https://github.com/intel-ai/hdk/blob/main/omniscidb/QueryEngine/ExpressionRange.cpp#L547
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Looks like a bug we might hit someday. I guess the referenced handling should go after the next if-statement, not before.
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Hah, you're probably right. I'll try it in a separate branch.
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Support join on rowid by skipping the hash table build and computing the row offset in the probe. Offset computation consists of null handling and range handling. For an empty table, we use roughly the expression range of (0, -1) which always returns -1 inside the newly added
rowid_hash_join_idxruntime function.There is one limitation -- because of this approach of not building the table we cannot support a query of the form
t1.rowid = t2.rowid AND ..... Loop joins still work of course. If this query becomes something we need to support with hash join, we can push the secondary join expression into filters and run a mini-loop join on each row that passes the rowid "hash".Added a bunch of tests but could probably use some more coverage. Open to ideas. The way I force the hash table builder to skip the build is by marking it empty during construction. This is kind of a hack, but I think it's ok for now with the checks I've added.
Closes #165