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https://issues.apache.org/jira/browse/DRILL-6099?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16381616#comment-16381616
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ASF GitHub Bot commented on DRILL-6099:
---------------------------------------
Github user amansinha100 commented on a diff in the pull request:
https://github.com/apache/drill/pull/1096#discussion_r171479641
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/common/DrillRelOptUtil.java
---
@@ -224,4 +226,64 @@ public Void visitInputRef(RexInputRef inputRef) {
}
}
+ public static boolean isLimit0(RexNode fetch) {
+ if (fetch != null && fetch.isA(SqlKind.LITERAL)) {
+ RexLiteral l = (RexLiteral) fetch;
+ switch (l.getTypeName()) {
+ case BIGINT:
+ case INTEGER:
+ case DECIMAL:
+ if (((long) l.getValue2()) == 0) {
+ return true;
+ }
+ }
+ }
+ return false;
+ }
+
+ public static boolean isProjectOutputRowcountUnknown(RelNode project) {
+ assert project instanceof Project : "Rel is NOT an instance of
project!";
+ try {
+ RexVisitor<Void> visitor =
--- End diff --
Would FLATTEN ever occur within other expressions ? I believe it always
occurs as an independent expression. If that's the case, it seems to me that
having a visitor is overkill.. what do you think ? Even the original rewrite
from project to flatten just iterates over the project exprs here [1].
[1]
https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/planner/physical/visitor/RewriteProjectToFlatten.java#L77
> Drill does not push limit past project (flatten) if it cannot be pushed into
> scan
> ---------------------------------------------------------------------------------
>
> Key: DRILL-6099
> URL: https://issues.apache.org/jira/browse/DRILL-6099
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.12.0
> Reporter: Gautam Kumar Parai
> Assignee: Gautam Kumar Parai
> Priority: Major
> Fix For: 1.13.0
>
>
> It would be useful to have pushdown occur past flatten(project). Here is an
> example to illustrate the issue:
> {{explain plan without implementation for }}{{select name,
> flatten(categories) as category from dfs.`/tmp/t_json_20` LIMIT 1;}}
> {{DrillScreenRel}}{{ }}
> {{ DrillLimitRel(fetch=[1])}}{{ }}
> {{ DrillProjectRel(name=[$0], category=[FLATTEN($1)])}}
> {{ DrillScanRel(table=[[dfs, /tmp/t_json_20]], groupscan=[EasyGroupScan
> [selectionRoot=maprfs:/tmp/t_json_20, numFiles=1, columns=[`name`,
> `categories`], files=[maprfs:///tmp/t_json_20/0_0_0.json]]])}}
> =================================================================
> Content of 0_0_0.json
> =================================================================
> {
> "name" : "Eric Goldberg, MD",
> "categories" : [ "Doctors", "Health & Medical" ]
> } {
> "name" : "Pine Cone Restaurant",
> "categories" : [ "Restaurants" ]
> } {
> "name" : "Deforest Family Restaurant",
> "categories" : [ "American (Traditional)", "Restaurants" ]
> } {
> "name" : "Culver's",
> "categories" : [ "Food", "Ice Cream & Frozen Yogurt", "Fast Food",
> "Restaurants" ]
> } {
> "name" : "Chang Jiang Chinese Kitchen",
> "categories" : [ "Chinese", "Restaurants" ]
> }
>
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