Alessandro Solimando created CALCITE-4556:
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Summary: CalciteMetaImpl#createEmptyResultSet override of
(Avatica) MetaImpl#createEmptyResultSet should not pass a class instance to
CursorFactory#deduce
Key: CALCITE-4556
URL: https://issues.apache.org/jira/browse/CALCITE-4556
Project: Calcite
Issue Type: Bug
Components: jdbc-driver
Affects Versions: 1.26.0
Reporter: Alessandro Solimando
Assignee: Alessandro Solimando
Fix For: 1.27.0
In Avatica 1.18.0, `CursorFactory#deduce(List<ColumnMetaData> columns, Class
resultClazz)` introduces a validation step requiring the names appearing in the
column metadata to match fields of `resultClazz`, whenever the class is not
null.
`CalciteMetaImpl#createEmptyResultSet` overrides
`MetaImpl#createEmptyResultSet` (class from Avatica), only to pass a value non
null value to the `resultClazz` argument.
Column metadata column names for Calcite internal metadata classes (_e.g._,
`MetaColumn`, `MetaCatalog`, `MetaSchema`, _etc_.) are built using
`MetaImpl#fieldMetadata` (transforming the name from camel case into
upper-snake case), violating the new contract of `deduce`.
This is not problematic, because `deduce` is only used to create an empty
result set, we are only interested in preserving the sought column names, which
is already the case for `MetaImpl#createEmptyResultSet`.
`CalciteMetaImpl#createEmptyResultSet`, if adapted to match the changes coming
from Avatica 1.18.0 would become identical to the
`MetaImpl#createEmptyResultSet` it overrides, and it should therefore be
removed.
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