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cap-js / cds-dbs

Monorepo for SQL Database Services for CAP
https://cap.cloud.sap/docs/
Apache License 2.0
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feat: simple queries #654

Closed BobdenOs closed 4 months ago

BobdenOs commented 4 months ago

Adds hana_simple_queries feature flag. Which will make @cap-js/hana run all possible queries without FOR JSON. Which allows hdb and @sap/hana-client to returns different results again.

Output converters are kept in place to reduce the likely hood of this happening. Current impacted test is Bookshop - Order By › collations for aggregating queries with subselect. Where the result of sum(price) as pri comes back as "150" for @sap/hana-client and "1.5e+2" for hdb. While expected is 150 in the FOR JSON result.

Additionally this PR removes the duplicate "_json_" output definition. Simplifying the SQL in all cases.

BobdenOs commented 4 months ago

This is for customers which believe these queries will be faster for their use cases. As the other databases are very fast in rendering json. There is no reason to do this. Also the output result is unstable.

oklemenz2 commented 4 months ago

@BobdenOs How is the case handled, where a query has an where ID in <array> clause. With new JSON concept only a single parameter was used and an json array was passed. Previously in old HANA adapter for each array entry a placeholder was used.

How is it now with your changes of this PR?

We liked the approach, that only a single placeholder is used because this would make the execution plan stable, no matter how many entries are in the array (which is often not under our control, as depending on user data)...

Having some toggles, that would provide different version would be good, so that we can experiment with that. For example also the Create was done with a single JSON object. How is this done now?

What do you think?

FYI @D069515