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https://issues.apache.org/jira/browse/PARQUET-2237?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17687131#comment-17687131
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ASF GitHub Bot commented on PARQUET-2237:
-----------------------------------------
yabola commented on code in PR #1023:
URL: https://github.com/apache/parquet-mr/pull/1023#discussion_r1102921044
##########
parquet-hadoop/src/main/java/org/apache/parquet/filter2/statisticslevel/StatisticsFilter.java:
##########
@@ -289,8 +320,14 @@ public <T extends Comparable<T>> Boolean visit(Lt<T> lt) {
T value = lt.getValue();
- // drop if value <= min
- return stats.compareMinToValue(value) >= 0;
+ // we are looking for records where v < someValue
+ if (stats.compareMinToValue(value) >= 0) {
+ // drop if value <= min
+ return BLOCK_CANNOT_MATCH;
+ } else {
+ // if value > min, we must take it
+ return BLOCK_MUST_MATCH;
Review Comment:
I think when `Statistics#hasNonNullValue` is true, it means that minMax is
generated by the data content, so it can represent the real data minMax (
`Statistics#hasNonNullValue` has been processed before.)
I think if we can use minMax to judge the `BLOCK_CANNOT_MATCH` , we can
also judge the `BLOCK_MUST_MATCH ` in some case.
> Improve performance when filters in RowGroupFilter can match exactly
> --------------------------------------------------------------------
>
> Key: PARQUET-2237
> URL: https://issues.apache.org/jira/browse/PARQUET-2237
> Project: Parquet
> Issue Type: Improvement
> Reporter: Mars
> Priority: Major
>
> If we can accurately judge by the minMax status, we don’t need to load the
> dictionary from filesystem and compare one by one anymore.
> Similarly , Bloomfilter needs to load from filesystem, it may costs time and
> memory. If we can exactly determine the existence/nonexistence of the value
> from minMax or dictionary filters , then we can avoid using Bloomfilter to
> Improve performance.
> For example,
> # read data greater than {{x1}} in the block, if minMax in status is all
> greater than {{{}x1{}}}, then we don't need to read dictionary and compare
> one by one.
> # If we already have page dictionaries and have compared one by one, we
> don't need to read BloomFilter and compare.
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