hqx871 commented on a change in pull request #2363:
URL: https://github.com/apache/calcite/pull/2363#discussion_r591354987
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File path: core/src/main/java/org/apache/calcite/rel/core/Sort.java
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@@ -124,11 +125,19 @@ public abstract Sort copy(RelTraitSet traitSet, RelNode
newInput,
@Override public @Nullable RelOptCost computeSelfCost(RelOptPlanner planner,
RelMetadataQuery mq) {
+ double rowCount = mq.getRowCount(this);
+ if (collation.getFieldCollations().isEmpty()) {
+ return planner.getCostFactory().makeCost(rowCount, 0, 0);
+ }
+ final int offsetValue = offset == null ? 0 : RexLiteral.intValue(offset);
+ final double inCount = mq.getRowCount(input);
// Higher cost if rows are wider discourages pushing a project through a
// sort.
- final double rowCount = mq.getRowCount(this);
final double bytesPerRow = getRowType().getFieldCount() * 4;
- final double cpu = Util.nLogN(rowCount) * bytesPerRow;
+ // When output count + offset is smaller than input count, we can use heap
sort,
+ // otherwise, we can use heap sort, quick sort and so on
+ final double heapSize = Math.min(rowCount + offsetValue, inCount);
Review comment:
I found duplicate code in EnumerableLimitSort. Shall I close the pr or
change the EnumerableLimitSort. code as follow
```
@Override public @Nullable RelOptCost computeSelfCost(RelOptPlanner planner,
RelMetadataQuery mq) {
final double rowCount = mq.getRowCount(this.input).doubleValue();
double toSort = getValue(this.fetch, rowCount);
if (this.offset != null) {
toSort += getValue(this.offset, rowCount);
}
// we need to sort at most rowCount rows
toSort = Math.min(rowCount, toSort);
// we need to process rowCount rows, and for every row
// we search the key in a TreeMap with at most toSort entries
final double lookup = Math.max(1., Math.log(toSort));
final double bytesPerRow = this.getRowType().getFieldCount() * 4.;
final double cpu = (rowCount * lookup) * bytesPerRow;
RelOptCost cost = planner.getCostFactory().makeCost(rowCount, cpu, 0);
return cost;
}
```
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