fix(sql): breaking💥 fix coalesce function correctness #4490
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this should be marked as a breaking change💥 |
bluestreak01
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ideoma
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May 17, 2024
core/src/main/java/io/questdb/griffin/engine/functions/bind/BindVariableServiceImpl.java
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core/src/test/java/io/questdb/test/cutlass/pgwire/PGJobContextTest.java
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ideoma
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core/src/test/java/io/questdb/test/griffin/WhereClauseParserTest.java
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ideoma
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May 20, 2024
ideoma
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[PR Coverage check]😍 pass : 771 / 872 (88.42%) file detail
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fixes #4478
fixes #4477
fixes #4505
Scope
This PR impacts all SQL functions that accept var-arg argument. More specifically impacted functions are:
Bind variable behaviour (general)
Bind variables are utilized by:
The prepared statement can be reused. Potentially allowing user to change bind variable type from one execution to the next.
Old behaviour
The affected functions use to accept bind variables and implicitly type them as
STRINGduring the preparation stage. When user sets type of bind variable as string, the result would be predictable. However, if user sets bind variable type to something other than string - the result is generally undefined. You can get anything between incorrect result and an obscure error.New behaviour
After SQL preparation stage the type of bind variables is UNDEFINED. The type becomes defined once bind variable is assigned a value. Some functions cannot allow that, because type of their arguments also influences the return type of the function itself. As a result these function no longer accept bind variables:
Additionally this function:
enforces the types of its arguments to be "compatible", e.g. to belong to the same group of types. The groups of types are:
arguments, which types belong to different groups will be rejected by `COALESCE
This function:
will now narrow down the type of bind variables to those compatible with the type of its left argument. The types must belong to the same group, as described for
COALESCE