yaooqinn opened a new pull request #26618: [SPARK-29980][SQL] Whitespaces handling for Cast and BinaryOperation between StringType and NumericTypes URL: https://github.com/apache/spark/pull/26618 <!-- 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? Here is a case, let see how it goes in different SQL engines. ```sql select cast('1 ' as int) as v1, '1 ' = 1 as v2 ``` #### spark 1.6 `NULL true` #### spark 2.1 `NULL true` #### spark 2.2 `NULL NULL` #### spark 2.3 `NULL NULL` #### spark 2.4 `NULL NULL` #### hive `NULL true` #### PostgreSQL ```sql postgres=# select cast('1 ' as int) as v1, '1 ' = 1 as v2; v1 | v2 ----+---- 1 | t (1 row) ``` #### presto ```sql presto> select cast('1 ' as int) as v1, '1 ' = 1 as v2; Query 20191120_060530_00002_f5kcs failed: line 1:38: '=' cannot be applied to varchar(2), integer select cast('1 ' as int) as v1, '1 ' = 1 as v2 presto> select cast('1 ' as int) as v1, '1 ' = '1 ' as v2; Query 20191120_060545_00003_f5kcs failed: Cannot cast '1 ' to INT ``` Our behavior is unstable because type coercion changed since 2.2. Personally, I think what PostgreSQL and Presto does here is more reasonable and consistent Currently, this pull request obeys PostgreSQL, might need further discussion against this behavior change. ### Why are the changes needed? For better dirty data auto handling, keep consistency with older version sparks ### Does this PR introduce any user-facing change? <!-- Yes, string will be trim at both ends before casting and compared to numerics ### 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. --> ad ut
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