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https://issues.apache.org/jira/browse/DERBY-1576?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Knut Anders Hatlen updated DERBY-1576:
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Attachment: d1576-4a.diff
The attached patch [^d1576-4a.diff] lifts the restriction that the case operand
cannot be an untyped parameter.
The original problem was that the case operand would forget its previously
inferred type each time it was rebound, so that its final type would be the
type of the last when operand, rather than the union of all the when operand
types.
The patch solves this by rewriting the query tree at the beginning of the bind
phase so that all occurrences of the case operand are replaced with dummy
parameter nodes, one dummy node per when clause in the case expression. This
way, when the when clauses are bound, each dummy parameter node is bound once,
so we avoid the problem with the previous type being forgotten when the node is
rebound.
At the end of the bind phase, we can go through the list of dummy nodes, find
the dominant type of those nodes, set the type of the case operand to that
type, and finally reinsert the case operand into the query tree.
The patch touches these files:
*impl/sql/compile/ConditionalNode.java*
- bindCaseOperand: Temporarily replace the case operand with dummy parameter
nodes.
- bindExpression: After binding the test conditions, check the types that the
dummy parameter nodes were bound to. If they are not compatible, raise an
error. If they are compatible, set the type of the case operand to the dominant
type, and reinsert it into the tree.
*impl/sql/compile/ReplaceNodeVisitor.java*
- New visitor implementation that replaces a node with some other node. Used
for reinserting the case operand into the tree.
*impl/sql/compile/ValueNodeList.java*
- getDominantTypeServices: Improve the method so that it works with lists that
consists entirely of nodes that require type from context, as long as they
already have been bound to a type.
*loc/messages.xml*
*shared/common/reference/SQLState.java*
- Remove the error message that used to be raised if the case operand was an
untyped parameter.
*tests/lang/CaseExpressionTest.java*
- Add tests that use untyped parameters in the case operand.
> Extend the CASE expression syntax for "simple case"
> ---------------------------------------------------
>
> Key: DERBY-1576
> URL: https://issues.apache.org/jira/browse/DERBY-1576
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Reporter: Christian d'Heureuse
> Assignee: Knut Anders Hatlen
> Priority: Minor
> Labels: derby_triage10_11
> Attachments: d1576-1a.diff, d1576-2a.diff, d1576-3a.diff,
> d1576-4a.diff, simple-simple.diff
>
>
> The ISO/IEC 9075-2:1999 SQL standard describes two kinds of CASE expressions:
> "simple case" and "searched case".
> The current Derby version supports "searched case" but not "simple case".
> The syntax for "simple case" is:
> CASE Expression
> WHEN Expression THEN Expression
> [ WHEN Expression THEN Expression ]
> ...
> ELSE ElseExpression
> END
> Example:
> VALUES
> CASE 4
> WHEN 1 THEN 'one'
> WHEN 2 THEN 'two'
> WHEN 3 THEN 'three'
> ELSE 'many'
> END
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