yaooqinn opened a new pull request #28106: [SPARK-31335][SQL] Add try function support URL: https://github.com/apache/spark/pull/28106 <!-- 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. 7. If you want to add a new configuration, please read the guideline first for naming configurations in 'core/src/main/scala/org/apache/spark/internal/config/ConfigEntry.scala'. --> ### What changes were proposed in this pull request? Add a TRY function that evaluates an expression and handles certain types of execution errors by returning NULL. In cases where it is preferable that queries produce NULL instead of failing when corrupt or invalid data is encountered, the TRY function may be useful especially when ANSI mode is on and the users need null-tolerant on certain columns or outputs. AnalysisExceptions will not handle by this, typically errors handled by TRY function are: * Division by zero, * Invalid casting, * Numeric value out of range, * e.t.c ### Why are the changes needed? In most cases of ANSI mode and few scenarios of non-ANSI mode, we will fail when an expression meets invalid or corrupt data. This behavior covers the whole SQL lifecycle and outputs. This is not very flexible for users when there are not ALL columns need to be that much strict, e.g. e.g. ```sql select cast(str1 as timestamp) as start, cast(str2 as timestamp) as end, cast(str3 as timestamp) as comment from .... ``` the `cast(str3 as timestamp) as comment` may not be that important to fail the entire query, then we can use `try(cast(str3 as timestamp)) as comment` to make it nullable. ### 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, add a new try function support. ### 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. --> add uts
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