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https://issues.apache.org/jira/browse/DERBY-6263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13686495#comment-13686495
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Knut Anders Hatlen commented on DERBY-6263:
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I agree that it sounds better to have the logic for skipping the nodes in the
visitor. Having logic in the accept methods that makes them behave differently
depending on which kind of visitor is used, sounds like a breach of the visitor
pattern. The Visitor interface has a skipChildren(Visitable) method for this
purpose.
The code for traversing the orderByLists array seems to assume that
(orderByLists[0] == null) == (orderByLists[i] == null) for all i. I'm not sure
that's guaranteed, so it might be safer to go through all elements of the array
and check each of them for being null.
> Make acceptChildren() overloads visit all clauses in QueryTreeNodes
> -------------------------------------------------------------------
>
> Key: DERBY-6263
> URL: https://issues.apache.org/jira/browse/DERBY-6263
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.11.0.0
> Reporter: Rick Hillegas
> Attachments: derby-6263-01-aa-visit-ignored-clauses.diff,
> derby-6263-02-aa-ignored-clauses-in-SelectNode.diff
>
>
> The acceptChildren() overloads don't visit all of the clauses in an AST node.
> This is probably a mistake. However, fixing it will require a systematic
> analysis of the AST nodes and probably some changes to the Visitors. Some
> queries rely on the fact that certain Visitors will not be called on some AST
> nodes even though the Visitors are called on sister nodes in the same parent
> AST node.
> An example of this defect is the CursorNode. If you call treePrint() on a
> CursorNode, you will see information on ORDER BY, FETCH, and OFFSET clauses.
> However, these clauses are not visited by CursorNode.acceptChildren(). This
> looks like an omission. This defect was brought to our attention by this
> email thread:
> http://apache-database.10148.n7.nabble.com/Using-ASTParser-and-TreeWalker-for-parsing-SQL-query-td131219.html.
> You can see the difference in treePrint() and acceptChildren() behavior by
> running the following query through the ASTParser and TreePrinter tools
> attached to DERBY-3946:
> select tablename from sys.systables where 1=2 order by tablename;
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