[CALCITE-815] Add an option to allow empty strings to represent null values #4462
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| boolean supportsUnsignedTypes(); | ||
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| /** | ||
| * Whether to convert empty string to null.. |
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I'll remove the redundant .
| public static final SqlFunction LTRIM = | ||
| SqlBasicFunction.create(SqlKind.LTRIM, | ||
| ReturnTypes.ARG0.andThen(SqlTypeTransforms.TO_NULLABLE) | ||
| ReturnTypes.ARG0.andThen(SqlTypeTransforms.FORCE_NULLABLE) |
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Is it only possible to change this in the Oracle mode here?
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Yes, this makes the functions return null even if no argements is null.
| * {@link SqlConformanceEnum#ORACLE_12}; | ||
| * false otherwise. | ||
| */ | ||
| boolean emptyStringIsNull(); |
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This is discussed in JIRA, I think emptyStringIsNull is OK.
| // Translate | ||
| // LTRIM/RTRIM(operand0[,operand1,...]) | ||
| // | ||
| // to the following if we want Oracle semantics |
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Here, we convert LTRIM(A) to the following expression: CASE WHEN LTRIM(A) = '' THEN NULL ELSE LTRIM(A) END. LTRIM(A) is calculated multiple times. If LTRIM(A) is a non-deterministic function, it may lead to an uncontrolled final result.
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Here, we convert LTRIM(A) to the following expression: CASE WHEN LTRIM(A) = '' THEN NULL ELSE LTRIM(A) END. LTRIM(A) is calculated multiple times. If LTRIM(A) is a non-deterministic function, it may lead to an uncontrolled final result.
Nondeterministic is not allowed during runtime, I've added some tests and throw exception when it occurs.
| return rexBuilder.makeCall(pos, SqlStdOperatorTable.CASE, | ||
| rexBuilder.makeCall(pos, SqlStdOperatorTable.EQUALS, rawCall, | ||
| rexBuilder.makeLiteral("")), | ||
| rexBuilder.makeNullLiteral(typeFactory.createSqlType(SqlTypeName.NULL)), |
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The NULL type here should be the same as that of LTRIM(A)
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Done, NULL type now is consistent with call's.
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This pull request has been marked as stale due to 30 days of inactivity. It will be closed in 90 days if no further activity occurs. If you think that’s incorrect or this pull request requires a review, please simply write any comment. If closed, you can revive the PR at any time and @mention a reviewer or discuss it on the dev@calcite.apache.org list. Thank you for your contributions. |
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This pull request has been marked as stale due to 30 days of inactivity. It will be closed in 90 days if no further activity occurs. If you think that’s incorrect or this pull request requires a review, please simply write any comment. If closed, you can revive the PR at any time and @mention a reviewer or discuss it on the dev@calcite.apache.org list. Thank you for your contributions. |
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The following functions will return null if the result is an empty string under Oracle semantics: