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Posted to reviews@spark.apache.org by "yaooqinn (via GitHub)" <gi...@apache.org> on 2024/01/30 07:24:10 UTC

[PR] [SPARK-46747][SQL] Avoid scan in getTableExistsQuery for JDBC Dialects [spark]

yaooqinn opened a new pull request, #44948:
URL: https://github.com/apache/spark/pull/44948

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   [SPARK-46747](https://issues.apache.org/jira/browse/SPARK-46747) reported an issue that Postgres instances suffered from too many shared locks, which was caused by Sparkā€˜s get table exist query. In this PR, we supplanted "SELECT 1 FROM $table LIMIT 1"` with `"SELECT 1 FROM $table WHERE 1=0"` to prevent data from being scanned.
   
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   overhead reduction for JDBC datasources
   
   ### Does this PR introduce _any_ user-facing change?
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   no
   
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   existing JDBC v1/v2 datasouce tests.
   
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   no


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Re: [PR] [SPARK-46747][SQL] Avoid scan in getTableExistsQuery for JDBC Dialects [spark]

Posted by "bala-bellam (via GitHub)" <gi...@apache.org>.
bala-bellam commented on PR #44948:
URL: https://github.com/apache/spark/pull/44948#issuecomment-1921828574

   Thank you @yaooqinn . Really appreciate the quick revert on this.
   
   We are bound to older version because we are stuck with EMR. And we have been moving to EMR 6.8, which comes with 3.3.0. 
   
   These locks are really killing us as we have a few tables having thousands of partitions, we are working on finding some alternatives. 


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Re: [PR] [SPARK-46747][SQL] Avoid scan in getTableExistsQuery for JDBC Dialects [spark]

Posted by "bala-bellam (via GitHub)" <gi...@apache.org>.
bala-bellam commented on PR #44948:
URL: https://github.com/apache/spark/pull/44948#issuecomment-1916829355

   Thank you @yaooqinn , @dongjoon-hyun . Can this patch be pushed to older versions as well, thank you.


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Re: [PR] [SPARK-46747][SQL] Avoid scan in getTableExistsQuery for JDBC Dialects [spark]

Posted by "yaooqinn (via GitHub)" <gi...@apache.org>.
yaooqinn closed pull request #44948: [SPARK-46747][SQL] Avoid scan in getTableExistsQuery for JDBC Dialects
URL: https://github.com/apache/spark/pull/44948


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Re: [PR] [SPARK-46747][SQL] Avoid scan in getTableExistsQuery for JDBC Dialects [spark]

Posted by "dongjoon-hyun (via GitHub)" <gi...@apache.org>.
dongjoon-hyun commented on PR #44948:
URL: https://github.com/apache/spark/pull/44948#issuecomment-1921876371

   That's too bad. 
   > We are bound to older version because we are stuck with EMR. And we have been moving to EMR 6.8, which comes with 3.3.0.
   
   However, the latest EMR also provides Spark 3.5.0 (emr-7.0.0) and (Spark 3.4.1) emr-6.15.0. I believe AWS support team is capable of delivering next Apache Spark releases without any issues.
   - https://docs.aws.amazon.com/emr/latest/ReleaseGuide/emr-spark.html
   
   Given that the situation, it seems that you have another non-Spark blocker issues in your production to block you from upgrading your EMR. Please try to fix it first. You need to catch up the latest EMP and Spark version first while you are waiting, @bala-bellam .


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