feat(optimizer): support PullUpCorrelatedPredicateAggRule #15026
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chenzl25
commented
Feb 6, 2024
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| └─LogicalProject { exprs: [ps_partkey, ps_suppkey, (0.5:Decimal * sum(l_quantity)) as $expr2] } | ||
| └─LogicalAgg { group_key: [ps_partkey, ps_suppkey], aggs: [sum(l_quantity)] } | ||
| └─LogicalJoin { type: LeftOuter, on: IsNotDistinctFrom(ps_partkey, l_partkey) AND IsNotDistinctFrom(ps_suppkey, l_suppkey), output: [ps_partkey, ps_suppkey, l_quantity] } | ||
| ├─LogicalAgg { group_key: [ps_partkey, ps_suppkey], aggs: [] } | ||
| │ └─LogicalJoin { type: LeftSemi, on: (ps_partkey = p_partkey), output: [ps_partkey, ps_suppkey] } | ||
| │ ├─LogicalSource { source: partsupp, columns: [ps_partkey, ps_suppkey, ps_availqty, ps_supplycost, ps_comment, _row_id], time_range: (Unbounded, Unbounded) } | ||
| │ └─LogicalProject { exprs: [p_partkey] } | ||
| │ └─LogicalSource { source: part, columns: [p_partkey, p_name, p_mfgr, p_brand, p_type, p_size, p_container, p_retailprice, p_comment, _row_id], time_range: (Unbounded, Unbounded) } | ||
| └─LogicalProject { exprs: [l_partkey, l_suppkey, l_quantity] } | ||
| └─LogicalFilter { predicate: IsNotNull(l_partkey) AND IsNotNull(l_suppkey) } | ||
| └─LogicalSource { source: lineitem, columns: [l_orderkey, l_partkey, l_suppkey, l_linenumber, l_quantity, l_extendedprice, l_discount, l_tax, l_returnflag, l_linestatus, l_shipdate, l_commitdate, l_receiptdate, l_shipinstruct, l_shipmode, l_comment, _row_id], time_range: (Unbounded, Unbounded) } | ||
| └─LogicalProject { exprs: [(0.5:Decimal * sum(l_quantity)) as $expr2, l_partkey, l_suppkey] } | ||
| └─LogicalAgg { group_key: [l_partkey, l_suppkey], aggs: [sum(l_quantity)] } | ||
| └─LogicalSource { source: lineitem, columns: [l_orderkey, l_partkey, l_suppkey, l_linenumber, l_quantity, l_extendedprice, l_discount, l_tax, l_returnflag, l_linestatus, l_shipdate, l_commitdate, l_receiptdate, l_shipinstruct, l_shipmode, l_comment, _row_id], time_range: (Unbounded, Unbounded) } |
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That is the TPCH Q20 we want to optimize in this PR.
chenzl25
commented
Feb 6, 2024
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| /// Pull up correlated predicates from the right agg side of Apply to the `on` clause of Join. | ||
| /// | ||
| /// Before: | ||
| /// | ||
| /// ```text | ||
| /// LogicalApply | ||
| /// / \ | ||
| /// LHS Project | ||
| /// | | ||
| /// Agg [group by nothing] | ||
| /// | | ||
| /// Project | ||
| /// | | ||
| /// Filter [correlated_input_ref(yyy) = xxx] | ||
| /// ``` | ||
| /// | ||
| /// After: | ||
| /// | ||
| /// ```text | ||
| /// LogicalApply [yyy = xxx] | ||
| /// / \ | ||
| /// LHS Project | ||
| /// | | ||
| /// Agg [group by xxx] | ||
| /// | | ||
| /// Project | ||
| /// | | ||
| /// Filter | ||
| /// ``` |
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A graph to explain how this rule works. It tries to pull up the correlated expr from the filter to the apply.
lmatz
approved these changes
Feb 6, 2024
st1page
approved these changes
Feb 6, 2024
st1page
approved these changes
Feb 6, 2024
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| // It could be too restrictive to require the group key to be empty. We can relax this in the future if necessary. | ||
| if !group_key.is_empty() { | ||
| return None; | ||
| } |
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is simply adding tge correlated key(xxx) into the group key correct?
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No, simply adding those group keys is not correct. We need to handle the new_agg parent input reference in a more sophisticated way instead of the current simple shifting.
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| // If there is a count aggregate, bail out and leave for general subquery unnesting to deal. | ||
| if agg_calls | ||
| .iter() | ||
| .any(|agg_call| agg_call.agg_kind == AggKind::Count) | ||
| { | ||
| return None; | ||
| }; |
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why? is count very special here?
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Yes, here is the corner case. I didn't come up with an idea of how to deal with it now. If you have some ideas, feel free to share. It is also related to the TPCH Q17.
create table t (a int, b int);
create table t2 (c int, d int);
insert into t values (1, 2);
flush;
select * from t where t.a > (select count(*) from t2 where b = d);There was a problem hiding this comment.
When group by is empty, count would return 0 instead of null.
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Yes, I can not find a way to rewrite it... But it should ok for Q17 because the aggregator is an AVG, we should choose one to optimize #14799
- maintain the AVG and other similar aggregator in plan node and delay their rewriting(currently RW rewrites it when creating the Agg plan node)
- consider the project-agg together in the rule later
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What's changed and what's your intention?
PullUpCorrelatedPredicateAggRuleto unnest a common subquery pattern in tpch. Pull up correlated predicates from the right agg side of Apply to theonclause of Join.Checklist
./risedev check(or alias,./risedev c)Documentation
Release note
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