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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-4879) Lookahead warning from ij.jj
Date Sun, 31 Oct 2010 19:22:25 GMT

     [ https://issues.apache.org/jira/browse/DERBY-4879?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Knut Anders Hatlen updated DERBY-4879:

    Attachment: ij.diff

Attaching a patch that reduces the lookahead in ij.jj from 2 to 1, thereby enabling lookahead
adequacy checking and silencing the warning. The following grammar changes were needed to
make it work with lookahead 1:

1) Remove the duplicate reference to FirstStatement in the grammar

2) Refactor the ConnectStatement rule so that it doesn't branch until after the common prefix
<CONNECT> has been seen

3) dynamicConnection/attributeList: Add a lookahead hint in attributeList to avoid ambiguity
when the attribute list is empty and followed by AS (as in CONNECT '...' ATTRIBUTES AS C1,
where a lookahead of 1 wouldn't be enough to determine whether AS was a property name or a

4) Merge the rules for qualified and unqualified table names in DescTableStatement

5) Factor out the common prefix <SHOW> in ShowStatement

6) Merge the rules IllegalStatementName and PrepareStatement into a single rule with the common
prefix <PREPARE> factored out

7) Merge the three rules JBMSPreparedStatementExec, F2KExecuteProcedure and ExecuteStatement
into a single rule, with the common prefix <EXECUTE> factored out

> Lookahead warning from ij.jj
> ----------------------------
>                 Key: DERBY-4879
>                 URL: https://issues.apache.org/jira/browse/DERBY-4879
>             Project: Derby
>          Issue Type: Improvement
>          Components: Tools
>    Affects Versions:
>            Reporter: Knut Anders Hatlen
>            Assignee: Knut Anders Hatlen
>            Priority: Minor
>         Attachments: ij.diff
> When building with "ant -q", I see this warning when JavaCC processes ij.jj:
>      [java] Warning: Lookahead adequacy checking not being performed since option LOOKAHEAD
is more than 1.  Set option FORCE_LA_CHECK to true to force checking.

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