perf: HANA list placeholder #380
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BobdenOs
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danjoa,
johannes-vogel and
stewsk
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…to hana-json-list
johannes-vogel
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Dec 15, 2023
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patricebender
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Jul 25, 2024
🤖 I have created a release *beep* *boop* --- <details><summary>db-service: 1.12.0</summary> ## [1.12.0](db-service-v1.11.0...db-service-v1.12.0) (2024-07-25) ### Fixed * see changelog ### Changed * generic-pool as real dep ([#750](#750)) ([b50c907](b50c907)) ### Performance Improvements * HANA list placeholder ([#380](#380)) ([3eadfea](3eadfea)) </details> <details><summary>postgres: 1.9.2</summary> ## [1.9.2](postgres-v1.9.1...postgres-v1.9.2) (2024-07-25) ### Changed * build script generates cds8 dependency in deployer app ([#758](#758)) ([5c21a67](5c21a67)) </details> <details><summary>hana: 1.1.1</summary> ## [1.1.1](hana-v1.1.0...hana-v1.1.1) (2024-07-25) ### Fixed * assocs with default value ([#752](#752)) ([a8660cf](a8660cf)) * make name for columns for ordinality unique ([#746](#746)) ([d3f9b23](d3f9b23)) </details> --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please). --------- Co-authored-by: Johannes Vogel <johannes.vogel@sap.com>
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Concept
HANA does a lot of preprocessing and optimization of queries. Which is cached and reused when the same SQL string is used. There is a limit to how many execution plans are cached by the HANA system. When reaching the cache limit queries will take much longer to execute. As new query executions will push out older caches. Resulting in the execution plan cache always being recalculated.
To prevent the execution plan cache from being exhausted it is important to produce the same SQL string as often as possible. There for this pull request fixes a core problem with the placeholder calculations. Additionally it checks any
listdefinitions forvalcontents. When it is determined that the list only consists ofvalit is converted into a JSON string and the SQL will contain aJSON_TABLEcall. This should produce the same SQL string Independent of the number of entries in thelist. Reducing the size of the SQL string and number of cached execution plans.