[Coral-Incremental] Cost calculation for RelNode #516
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yyy1000
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yyy1000
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Jul 10, 2024
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| public CostInfo getExecutionCost(RelNode rel) { | ||
| if (rel instanceof TableScan) { | ||
| return getExecutionCostTableScan((TableScan) rel); | ||
| } else if (rel instanceof LogicalJoin) { | ||
| return getExecutionCostJoin((LogicalJoin) rel); | ||
| } else if (rel instanceof LogicalUnion) { | ||
| return getExecutionCostUnion((LogicalUnion) rel); | ||
| } else if (rel instanceof LogicalProject) { | ||
| return getExecutionCostProject((LogicalProject) rel); | ||
| } | ||
| return new CostInfo(0.0, 0.0); | ||
| } |
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This is the core cost calculation framework.
It
- Walk through the whole RelNode tree and get the cost
- Keep the Row Count Information which will be used for IO cost
coral-incremental/src/main/java/com/linkedin/coral/incremental/RelNodeCostEstimator.java
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| } | ||
| } | ||
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| private Double estimateJoinSelectivity(List<JoinKey> joinKeys) { |
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I didn't write the logic now,
it will be from the join key, and from the statistic map info like distinct/row_count to get Selectivity
yyy1000
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yyy1000
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yyy1000
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KevinGe00
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Jul 26, 2024
coral-incremental/src/main/java/com/linkedin/coral/incremental/RelNodeCostEstimator.java
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coral-incremental/src/main/java/com/linkedin/coral/incremental/RelNodeCostEstimator.java
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coral-incremental/src/main/java/com/linkedin/coral/incremental/RelNodeCostEstimator.java
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coral-incremental/src/main/java/com/linkedin/coral/incremental/RelNodeCostEstimator.java
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coral-incremental/src/main/java/com/linkedin/coral/incremental/RelNodeCostEstimator.java
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coral-incremental/src/main/java/com/linkedin/coral/incremental/RelNodeCostEstimator.java
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coral-incremental/src/main/java/com/linkedin/coral/incremental/RelNodeCostEstimator.java
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coral-incremental/src/main/java/com/linkedin/coral/incremental/RelNodeCostEstimator.java
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| private CostInfo getExecutionCostJoin(LogicalJoin join) { | ||
| RelNode left = join.getLeft(); | ||
| RelNode right = join.getRight(); | ||
| if (!(left instanceof TableScan) || !(right instanceof TableScan)) { |
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Are expanding the cost estimator to handle joins for more than 2 tables?
Co-authored-by: Kevin Ge <[email protected]>
yyy1000
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KevinGe00
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Jul 29, 2024
coral-incremental/src/main/java/com/linkedin/coral/incremental/RelNodeCostEstimator.java
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coral-incremental/src/test/java/com/linkedin/coral/incremental/RelNodeCostEstimatorTest.java
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coral-incremental/src/main/java/com/linkedin/coral/incremental/TableStatistic.java
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|
Overall feedback is that I believe the PR sounds too specific and there is no general framework for cost estimation that is applicable to various operators by specializing some of its aspects. I think we need to iterate over this PR to make it more abstract with various implementations. This may be better discussed over a doc. |
wmoustafa
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Aug 2, 2024
| // The number of rows in the table | ||
| Double rowCount; | ||
| // The number of distinct values in each column | ||
| Map<String, Double> distinctCountByRow; |
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Does this work for nested columns? If yes, what is the spec of the key?
Does it work for complex types?
If the answer is no, we should be explicit about this at least in the Java doc.
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| // The shuffle cost of a join is the maximum shuffle cost of its children because | ||
| // in modern distributed systems, the shuffle cost is dominated by the largest shuffle. |
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Terminology is not clear here. What is the shuffle cost of children? We might need to discuss this over a doc.
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What changes are proposed in this pull request, and why are they necessary?
The goal of this PR is to introduce cost calculation method for Coral Incremental module, that's given an Input RelNode, return its cost for {executing it and writing the result into output}. So, for two RelNodes, one is incremental format, and the other is batch format, we could choose one with less cost, which could have better performance when executing.
The main changes are:
How was this patch tested?
Unit test