Add PushdownTopN through Project and Outer Join rules #419

kasiafi · 2019-03-09T16:57:06Z

instead of #220

sopel39

LGTM % add tests

sopel39 · 2019-03-11T09:54:30Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+            topN()
+                    .with(source().matching(
+                            project()
+                                    .matching(projectNode -> !projectNode.isIdentity())


why not? because optimizer would loop forever?

Correct, same is here: io.prestosql.sql.planner.iterative.rule.PushLimitThroughProject

Please, add a comment about this.

nit: not(ProjectNode::isIdentity)

which not did you mean?

https://google.github.io/guava/releases/23.0/api/docs/com/google/common/base/Predicates.html#not-com.google.common.base.Predicate-

sopel39 · 2019-03-11T10:03:44Z

...main/src/test/java/io/prestosql/sql/planner/iterative/rule/TestPushTopNThroughOuterJoin.java

+        extends BaseRuleTest
+{
+    @Test
+    public void testPushTopNThroughLeftJoin()


you could also add test when top n has key from left and right side so it cannot be pushed to any side.

sopel39 · 2019-03-11T10:05:25Z

...main/src/test/java/io/prestosql/sql/planner/iterative/rule/TestPushTopNThroughOuterJoin.java

+    @Test
+    public void testPushTopNThroughLeftJoin()
+    {
+        tester().assertThat(new PushTopNThroughOuterJoin())


please also add test to TestLogicalPlanner so that we can see that the rules indeed work in actual plan (e.g: top n is pushed down through projection and join)

kokosing · 2019-03-11T10:42:34Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+            topN()
+                    .with(source().matching(
+                            project()
+                                    .matching(projectNode -> !projectNode.isIdentity())


Correct, same is here: io.prestosql.sql.planner.iterative.rule.PushLimitThroughProject

kokosing · 2019-03-11T10:44:00Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+                            project()
+                                    .matching(projectNode -> !projectNode.isIdentity())
+                                    .capturedAs(PROJECT_CHILD)
+                                    .with(source().matching(node -> !(node instanceof TableScanNode) && !(node instanceof FilterNode)))));


This is not correct. If there is no table scan behind filter node, then you could push TopN. So you need to check the child of filter node.

I understand it could be difficult to do in pattern, so maybe you could move it to apply.

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

kasiafi · 2019-03-12T06:59:52Z

Applied comments.

kokosing · 2019-03-12T09:41:16Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughOuterJoin.java

+                .orElseGet(Result::empty);
+    }
+
+    private static Optional<JoinNode> joinNodeWithTopNSource(TopNNode topNNode, JoinNode joinNode, Context context)


please inline this method

kokosing · 2019-03-12T09:42:46Z

presto-main/src/main/java/io/prestosql/sql/planner/optimizations/QueryCardinalityUtil.java

+                upper = min(sourceCardinalityRange.upperEndpoint(), node.getCount());
+            }
+            long lower = min(upper, sourceCardinalityRange.lowerEndpoint());
+            return Range.closed(lower, upper);


Can we reuse code of visitLimit instead of copying.

kokosing · 2019-03-12T09:43:20Z

presto-main/src/main/java/io/prestosql/sql/planner/plan/JoinNode.java

@@ -299,7 +299,7 @@ public PlanNode getRight()
    }

    @Override
-    public PlanNode replaceChildren(List<PlanNode> newChildren)
+    public JoinNode replaceChildren(List<PlanNode> newChildren)


kokosing · 2019-03-12T09:47:46Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+
+        PlanNode projectSource = context.getLookup().resolveGroup(projectNode.getSource()).findFirst().orElseThrow(IllegalStateException::new);
+        if (projectSource instanceof FilterNode) {
+            PlanNode filterSource = context.getLookup().resolveGroup(((FilterNode) projectSource).getSource()).findFirst().orElseThrow(IllegalStateException::new);


Please format this as:

PlanNode filterSource = context.getLookup().resolveGroup(((FilterNode) projectSource).getSource()) .findFirst() .orElseThrow(IllegalStateException::new);

Same above.

Also instead of findFirst you should use com.google.common.collect.MoreCollectors#toOptional.

Lookup#resolveGroup followed by .findFirst() (or toOptional) is only pretending we support non-single element groups here.
It would be way better to use the (deprecated) io.prestosql.sql.planner.iterative.Lookup#resolve directly instead of pretending we do something better.

sopel39 · 2019-03-12T10:01:20Z

presto-main/src/test/java/io/prestosql/sql/planner/TestLogicalPlanner.java

+                                        anyTree(
+                                                join(LEFT, ImmutableList.of(equiJoinClause("N_KEY", "R_KEY")),
+                                                        project(
+                                                                topN(1, ImmutableList.of(sort("N_COMM", ASCENDING, LAST)), TopNNode.Step.PARTIAL,


put each argument in new line

I tried to follow the formatting used in this class.

sopel39 · 2019-03-12T10:01:27Z

presto-main/src/test/java/io/prestosql/sql/planner/TestLogicalPlanner.java

+        assertPlan("SELECT n.name, r.name FROM nation n LEFT JOIN region r ON n.regionkey = r.regionkey ORDER BY n.comment LIMIT 1",
+                anyTree(
+                        project(
+                                topN(1, ImmutableList.of(sort("N_COMM", ASCENDING, LAST)), TopNNode.Step.FINAL,


martint

Some minor comments and a question.

martint · 2019-03-13T03:03:35Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughOuterJoin.java

+
+    private static final Pattern<TopNNode> PATTERN =
+            topN().with(source().matching(
+                    join().capturedAs(JOIN_CHILD).with(type().matching(type -> isLeftOrFullOuter(type) || isRightOrFullOuter(type)))));


I think this expression makes it harder to reason about what this is doing that it should: isLeftOrFullOuter(type) || isRightOrFullOuter(type). It's really just saying "is it an outer join?". So, I'd just replace this with: type == LEFT || type == RIGHT || type == FULL

martint · 2019-03-13T03:04:47Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughOuterJoin.java

+        return cardinality.hasUpperBound() && cardinality.upperEndpoint() <= limit;
+    }
+
+    private static boolean isLeftOrFullOuter(JoinNode.Type type)


I don't think these methods make the code more readable. They say exactly what the condition expresses, so they are not hiding complexity. I'd just inline them

martint · 2019-03-13T03:05:40Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+            topN()
+                    .with(source().matching(
+                            project()
+                                    .matching(projectNode -> !projectNode.isIdentity())


Please, add a comment about this.

martint · 2019-03-13T03:08:41Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+        if (projectSource instanceof FilterNode) {
+            PlanNode filterSource = context.getLookup().resolve(((FilterNode) projectSource).getSource());
+            if (filterSource instanceof TableScanNode) {
+                return Result.empty();


Why do we limit this case? I would think this rule should not care about whether there's a TableScan or Filter involved.

also, there's another limitation in the PATTERN, which says that there cannot be a TableScanNode as a source of the Projection. Probably both limitations should go to apply() for symmetry.

Why do we limit this case?

I was about to ask @sopel39 and @kokosing about that, because it was their request. I want to add some explanatory comment.

@martint if you push topN below projection that is above filter or table scan then such projection won't be merged as a single PageProcessor with filter or/and table scan.

If such topN node is PARTIAL and we have a lot of splits then it could potentially be more expensive to split projection from filter. What do you think?

also, there's another limitation in the PATTERN, which says that there cannot be a TableScanNode as a source of the Projection. Probably both limitations should go to apply() for symmetry.

It's fine to have different but complementary constraints in the pattern vs in apply. Sometimes there are complex cases that cannot be easily described in terms of patterns. But if they can, there's better opportunity for the pattern matcher to do it more efficiently.

I want to add some explanatory comment.

Yes, please do! My general rule of thumb is "if I were to look at some code I wrote a few months down the road, would I be able to figure out what it's doing or the motivation?". If not, a comment is warranted. In this case, it's not entirely obvious why this pattern is excluded, so let's add an explanation.

martint · 2019-03-13T03:08:59Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+
+        TopNNode mappedTopN = symbolMapper.get().map(parent, projectNode.getSource(), context.getIdAllocator().getNextId());
+
+        return Result.ofPlanNode(


All these can go in the same line.

sopel39 · 2019-03-13T10:03:50Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughOuterJoin.java

+    @Override
+    public Result apply(TopNNode parent, Captures captures, Context context)
+    {
+        JoinNode joinNode = captures.get(JOIN_CHILD);


if the parent TopN is PARTIAL then it should be fully pushed down below join

Actually. Make this rule only execute for PARTIAL TopN nodes as TopN split happens in CreatePartialTopN

sopel39 · 2019-03-13T10:08:53Z

presto-main/src/main/java/io/prestosql/sql/planner/PlanOptimizers.java

@@ -290,6 +292,8 @@ public PlanOptimizers(
                                        new PushLimitThroughMarkDistinct(),
                                        new PushLimitThroughOuterJoin(),
                                        new PushLimitThroughSemiJoin(),
+                                        new PushTopNThroughProject(),
+                                        new PushTopNThroughOuterJoin(),


PushTopNThroughOuterJoin should be only executed with

builder.add(new IterativeOptimizer( ruleStats, statsCalculator, estimatedExchangesCostCalculator, ImmutableSet.of( new CreatePartialTopN(), new PushTopNThroughUnion())));

PushTopNThroughProject should be executed here and together with PushTopNThroughOuterJoin

Why move PushTopNThroughProject and PushTopNThroughOuterJoin there? Don't they belong together with PushLimitThroughProject and PushLimitThroughOuterJoin?

Why move PushTopNThroughProject and PushTopNThroughOuterJoin there?

It is because in that section partial TopN nodes are created via CreatePartialTopN() rule. There is already PushTopNThroughUnion() rule there that pushes partial aggregations though union.

sopel39

some more comments

more comments

kasiafi · 2019-03-22T08:06:36Z

Applied comments.

kokosing · 2019-03-22T08:55:37Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+ * <pre>
+ * - TopN
+ *    - Project (non-identity)
+ *       - Source other than Filter(TableScan) / TableScan


replace / with or

kokosing · 2019-03-22T08:56:37Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+            topN()
+                    .with(source().matching(
+                            project()
+                                    .matching(projectNode -> !projectNode.isIdentity())


nit: not(ProjectNode::isIdentity)

kokosing · 2019-03-22T08:57:52Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+                                    .matching(projectNode -> !projectNode.isIdentity())
+                                    .capturedAs(PROJECT_CHILD)
+                                    // do not push topN between projection and table scan so that they can be merged into a PageProcessor
+                                    .with(source().matching(node -> !(node instanceof TableScanNode)))));


nit: There is io.prestosql.util.MorePredicates#isInstanceOfAny. Maybe we can add something like isNotInstanceOf there?

I think this could be taken care of in the future.

kokosing · 2019-03-22T08:58:30Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+        }
+
+        TopNNode mappedTopN = symbolMapper.get().map(parent, projectNode.getSource(), context.getIdAllocator().getNextId());
+


nit: not needed vertical space.

I would even inline mappedTopN

kokosing · 2019-03-22T09:00:30Z

...o-main/src/test/java/io/prestosql/sql/planner/iterative/rule/TestPushTopNThroughProject.java

+                            p.project(
+                                    Assignments.of(
+                                            projectedA, new SymbolReference("a"),
+                                            projectedC, new ArithmeticBinaryExpression(ADD, new SymbolReference("a"), new SymbolReference("b"))),


nit: expression("a + b")

kokosing · 2019-03-22T09:01:47Z

presto-main/src/main/java/io/prestosql/sql/planner/PlanOptimizers.java

@@ -438,7 +438,9 @@ public PlanOptimizers(
                estimatedExchangesCostCalculator,
                ImmutableSet.of(
                        new CreatePartialTopN(),
-                        new PushTopNThroughUnion())));
+                        new PushTopNThroughUnion(),
+                        new PushTopNThroughProject(),


this line belongs to previous commit.

kokosing · 2019-03-22T09:04:40Z

presto-main/src/main/java/io/prestosql/sql/planner/optimizations/QueryCardinalityUtil.java

+            return applyLimit(node.getSource(), node.getCount());
+        }
+
+        private Range<Long> applyLimit(PlanNode source, long limit)


nit: s/applyLimit/visitLimitSource ?

nit: s/applyLimit/visitLimitSource ?

I don't think we should rename it to visitXXX since it makes it easy to confuse with the methods that are implementations of the visitor interface. This is just an internal utility method.

kokosing · 2019-03-22T09:09:34Z

presto-main/src/test/java/io/prestosql/sql/planner/TestLogicalPlanner.java

+                                                        project(
+                                                                topN(1, ImmutableList.of(sort("N_COMM", ASCENDING, LAST)), TopNNode.Step.PARTIAL,
+                                                                        tableScan("nation", ImmutableMap.of("N_NAME", "name", "N_KEY", "regionkey", "N_COMM", "comment")))),
+                                                        anyTree(


Nits:

replace with anyNot(TopNode.class, anyTree(...))?
The best would be anyTreeNot(TopNode.class, tableScan(...)

can't find anyTreeNot()

Because it does not exists yet. It would be the best if it would have existed.

I think it could be added in another PR. I could give it a try later.

kasiafi · 2019-03-22T23:45:31Z

Applied some comments.

kasiafi · 2019-03-25T09:22:14Z

@martint do you have any more comments?

martint · 2019-03-25T21:37:02Z

presto-main/src/main/java/io/prestosql/sql/planner/optimizations/QueryCardinalityUtil.java

+            return applyLimit(node.getSource(), node.getCount());
+        }
+
+        private Range<Long> applyLimit(PlanNode source, long limit)


nit: s/applyLimit/visitLimitSource ?

I don't think we should rename it to visitXXX since it makes it easy to confuse with the methods that are implementations of the visitor interface. This is just an internal utility method.

kokosing · 2019-03-26T08:26:37Z

Merged, thanks!

findepi · 2021-02-25T08:44:00Z

presto-main/src/main/java/io/prestosql/sql/planner/iterative/rule/PushTopNThroughProject.java

+            topN()
+                    .with(source().matching(
+                            project()
+                                    // do not push topN through identity projection which could be there for column pruning purposes


Does it mean we need a Push TopN through Project into TableScan rule to fully leverage #6847?

cc @losipiuk @wendigo

We could potentially combine two rules into single one, e.g: try to pushdown though project and into connector

yeah, a rule set; i created #7029 for this, let's move discussion over there

cla-bot bot added the cla-signed label Mar 9, 2019

sopel39 previously approved these changes Mar 11, 2019

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kasiafi force-pushed the pushdownTopNThroughProjectOuter branch from 00c11cd to 1eeea6d Compare March 11, 2019 23:21

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kasiafi force-pushed the pushdownTopNThroughProjectOuter branch from 1eeea6d to f111645 Compare March 12, 2019 22:10

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kasiafi force-pushed the pushdownTopNThroughProjectOuter branch from f111645 to 3cd8d0a Compare March 21, 2019 21:11

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kasiafi added 2 commits March 22, 2019 23:20

Push TopN through Project

d22240c

Push TopN through outer Join

1d6480f

kasiafi force-pushed the pushdownTopNThroughProjectOuter branch from 3cd8d0a to 1d6480f Compare March 22, 2019 22:24

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kokosing merged commit ec57ed6 into trinodb:master Mar 26, 2019

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		TopNNode mappedTopN = symbolMapper.get().map(parent, projectNode.getSource(), context.getIdAllocator().getNextId());

		return Result.ofPlanNode(

Add PushdownTopN through Project and Outer Join rules #419

Add PushdownTopN through Project and Outer Join rules #419

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kasiafi commented Mar 9, 2019

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sopel39 Mar 13, 2019 • edited

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kasiafi commented Mar 22, 2019

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kasiafi commented Mar 22, 2019

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sopel39 Feb 25, 2021 • edited

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sopel39 Mar 13, 2019 •

edited

sopel39 Feb 25, 2021 •

edited