Ngone51 opened a new pull request #26463: [SPARK-29837][SLQ] PostgreSQL dialect: cast to boolean URL: https://github.com/apache/spark/pull/26463 <!-- Thanks for sending a pull request! Here are some tips for you: 1. If this is your first time, please read our contributor guidelines: https://spark.apache.org/contributing.html 2. Ensure you have added or run the appropriate tests for your PR: https://spark.apache.org/developer-tools.html 3. If the PR is unfinished, add '[WIP]' in your PR title, e.g., '[WIP][SPARK-XXXX] Your PR title ...'. 4. Be sure to keep the PR description updated to reflect all changes. 5. Please write your PR title to summarize what this PR proposes. 6. If possible, provide a concise example to reproduce the issue for a faster review. --> ### What changes were proposed in this pull request? <!-- Please clarify what changes you are proposing. The purpose of this section is to outline the changes and how this PR fixes the issue. If possible, please consider writing useful notes for better and faster reviews in your PR. See the examples below. 1. If you refactor some codes with changing classes, showing the class hierarchy will help reviewers. 2. If you fix some SQL features, you can provide some references of other DBMSes. 3. If there is design documentation, please add the link. 4. If there is a discussion in the mailing list, please add the link. --> Make SparkSQL's `cast to boolean` behavior be consistent with PostgreSQL when spark.sql.dialect is configured as PostgreSQL. ### Why are the changes needed? <!-- Please clarify why the changes are needed. For instance, 1. If you propose a new API, clarify the use case for a new API. 2. If you fix a bug, you can clarify why it is a bug. --> SparkSQL and PostgreSQL have a lot different cast behavior between types by default. We should make SparkSQL's cast behavior be consistent with PostgreSQL when `spark.sql.dialect` is configured as PostgreSQL. ### Does this PR introduce any user-facing change? <!-- If yes, please clarify the previous behavior and the change this PR proposes - provide the console output, description and/or an example to show the behavior difference if possible. If no, write 'No'. --> Yes. If user switches to PostgreSQL dialect now, they will * get an exception if they input a invalid string, e.g "erut", while they get `null` before; * get an exception if they input `TimestampType`, `DateType`, `LongType`, `ShortType`, `ByteType`, `DecimalType`, `DoubleType`, `FloatType` values, while they get `true` or `false` result before. And here're evidences for those unsupported types from PostgreSQL: timestamp: ``` postgres=# select cast(cast('2019-11-11' as timestamp) as boolean); ERROR: cannot cast type timestamp without time zone to boolean ``` date: ``` postgres=# select cast(cast('2019-11-11' as date) as boolean); ERROR: cannot cast type date to boolean ``` bigint: ``` postgres=# select cast(cast('20191111' as bigint) as boolean); ERROR: cannot cast type bigint to boolean ``` smallint: ``` postgres=# select cast(cast(2019 as smallint) as boolean); ERROR: cannot cast type smallint to boolean ``` bytea: ``` postgres=# select cast(cast('2019' as bytea) as boolean); ERROR: cannot cast type bytea to boolean ``` decimal: ``` postgres=# select cast(cast('2019' as decimal) as boolean); ERROR: cannot cast type numeric to boolean ``` float: ``` postgres=# select cast(cast('2019' as float) as boolean); ERROR: cannot cast type double precision to boolean ``` ### How was this patch tested? <!-- If tests were added, say they were added here. Please make sure to add some test cases that check the changes thoroughly including negative and positive cases if possible. If it was tested in a way different from regular unit tests, please clarify how you tested step by step, ideally copy and paste-able, so that other reviewers can test and check, and descendants can verify in the future. If tests were not added, please describe why they were not added and/or why it was difficult to add. --> Added and tested manually.
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