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impala
Peter Rozsa
IMPALA-12732: Add support for MERGE statements for Iceberg tables MERGE statement is a DML command that allows users to perform conditional insert, update, or delete operations on a target table based on the results of a join with a source table. This change adds MERGE statement parsing and an Iceberg-specific semantic analysis, planning, and execution. The parsing grammar follows the SQL standard, it accepts the same syntax as Hive, Spark, and Trino by supporting arbitrary number of WHEN clauses, with conditions or without and accepting inline views as source. Example: 'MERGE INTO target t USING source s ON t.id = s.id WHEN MATCHED AND t.id < 100 THEN UPDATE SET column1 = s.column1 WHEN MATCHED AND t.id > 100 THEN DELETE WHEN MATCHED THEN UPDATE SET column1 = "value" WHEN NOT MATCHED THEN INSERT VALUES (s.id, s.column1);' The Iceberg-specific analysis, planning, and execution are based on a concept that was previously used for UPDATE: The analyzer creates a SELECT statement with all target and source columns (including Iceberg's virtual columns) and a 'row_present' column that defines whether the source, the target, or both rows are present in the result set after joining the two table references by the ON clause. The join condition should be an equi-join, as it is a FULL OUTER JOIN, and Impala currently supports only equi-joins in this case. The joining order is forced by a query hint, this guarantees that the target table is always on the left side. A new, IcebergMergeNode is added at planning phase, this node does the row-level filtering for each MATCHED/ NOT MATCHED cases. The 'row_present' column decides which case group will be evaluated; if both sides are available, the matched cases, if only the source side matches then the not matched cases and their filter expressions will be evaluated over the row. If one of the cases match, then the execution evaluates the result expressions into the output row batch, and an auxiliary tuple will store the merge action. The merge action is a flag for the newly added IcebergMergeSink; this sink will route each incoming row from IcebergMergeNode to their respective destination. Each row could go to the delete sink, insert sink, or to both sinks. Target-side duplicate records are filtered during IcebergMergeNode's execution, if one target table-side duplicate is detected, the whole statement's execution is stopped and the error is reported back to the user. Added tests: - Parser tests - Analyzer tests - Unit test for WHEN NOT MATCHED INSERT column collation - Planner tests for partitioned/sorted cases - Authorization tests - E2E tests Change-Id: I3416a79740eddc446c87f72bf1a85ed3f71af268 Reviewed-on: http://gerrit.cloudera.org:8080/21423 Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com> Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
2 месяца назад История
README.md

Welcome to Impala

Lightning-fast, distributed SQL queries for petabytes of data stored in open data and table formats.

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:

More about Impala

The fastest way to try out Impala is a quickstart Docker container. You can try out running queries and processing data sets in Impala on a single machine without installing dependencies. It can automatically load test data sets into Apache Kudu and Apache Parquet formats and you can start playing around with Apache Impala SQL within minutes.

To learn more about Impala as a user or administrator, or to try Impala, 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. Impala supports x86_64 and has experimental support for arm64 (as of Impala 4.0). Impala Requirements contains more detailed information on the minimum CPU requirements.

Supported OS Distributions

Impala runs on Linux systems only. The supported distros are

  • Ubuntu 16.04/18.04
  • CentOS/RHEL 7/8

Other systems, e.g. SLES12, may also be supported but are not tested by the community.

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.

Описание

Apache Impala

C++
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