Github user amansinha100 commented on a diff in the pull request:
https://github.com/apache/drill/pull/1096#discussion_r171480227
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillPushLimitToScanRule.java
---
@@ -55,18 +62,21 @@ public void onMatch(RelOptRuleCall call) {
}
};
- public static DrillPushLimitToScanRule LIMIT_ON_PROJECT =
- new DrillPushLimitToScanRule(
- RelOptHelper.some(DrillLimitRel.class, RelOptHelper.some(
- DrillProjectRel.class,
RelOptHelper.any(DrillScanRel.class))),
- "DrillPushLimitToScanRule_LimitOnProject") {
+ public static DrillPushLimitToScanRule LIMIT_ON_PROJECT = new
DrillPushLimitToScanRule(
+ RelOptHelper.some(DrillLimitRel.class,
RelOptHelper.any(DrillProjectRel.class)),
"DrillPushLimitToScanRule_LimitOnProject") {
@Override
public boolean matches(RelOptRuleCall call) {
DrillLimitRel limitRel = call.rel(0);
- DrillScanRel scanRel = call.rel(2);
- // For now only applies to Parquet. And pushdown only apply limit
but not offset,
+ DrillProjectRel projectRel = call.rel(1);
+ // pushdown only apply limit but not offset,
// so if getFetch() return null no need to run this rule.
- if (scanRel.getGroupScan().supportsLimitPushdown() &&
(limitRel.getFetch() != null)) {
--- End diff --
One implication of this is suppose the underlying Scan does not support
Limit pushdown, you could end up with a plan `Scan->Limit->Project->Limit`
where the Limit above the Scan is redundant (assume that there is no FLATTEN in
this query). Can this be avoided ?
---
