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amansinha100 authored and Impala Public Jenkins committed 08a7569 Jul 2, 2020
IMPALA-9911: Fix IS [NOT] NULL predicate selectivity
When null count is 0, the IsNullPredicate's selectivity
was not being computed since it did not distinguish
between a -1 (no stats) vs a 0 null count. This caused
a default selectivity estimate being applied. This
patch fixes it by explicitly checking whether nulls
count stat is present and if so, use it regardless of
whether it is 0 or more.

Testing:
 - Added cardinality tests for IS NULL and IS NOT NULL.
 - Ran PlannerTest and updated baseline plans.
 - Updated expected selectivity for null predicate tests
   in ExprCardinalityTest.
 - Ran precommit tests through gerrit-verify-dryrun

Change-Id: I46c084be780b8f5aead9e2b9656fbab6cc8c8874
Reviewed-on: http://gerrit.cloudera.org:8080/16131
Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>

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README.md

Welcome to Impala

Lightning-fast, distributed SQL queries for petabytes of data stored in Apache Hadoop clusters.

Impala is a modern, massively-distributed, massively-parallel, C++ query engine that lets you analyze, transform and combine data from a variety of data sources:

  • Best of breed performance and scalability.
  • Support for data stored in HDFS, Apache HBase, Apache Kudu, Amazon S3, Azure Data Lake Storage, Apache Hadoop Ozone and more!
  • Wide analytic SQL support, including window functions and subqueries.
  • On-the-fly code generation using LLVM to generate lightning-fast code tailored specifically to each individual query.
  • Support for the most commonly-used Hadoop file formats, including Apache Parquet and Apache ORC.
  • Support for industry-standard security protocols, including Kerberos, LDAP and TLS.
  • Apache-licensed, 100% open source.

More about Impala

To learn more about Impala as a business user, or to try Impala live or in a VM, please visit the Impala homepage. Detailed documentation for administrators and users is available at Apache Impala documentation.

If you are interested in contributing to Impala as a developer, or learning more about Impala's internals and architecture, visit the Impala wiki.

Supported Platforms

Impala only supports Linux at the moment.

Export Control Notice

This distribution uses cryptographic software and may be subject to export controls. Please refer to EXPORT_CONTROL.md for more information.

Build Instructions

See Impala's developer documentation to get started.

Detailed build notes has some detailed information on the project layout and build.

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