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http://issues.apache.org/jira/browse/DERBY-1231?page=comments#action_12455556 ]
Knut Anders Hatlen commented on DERBY-1231:
-------------------------------------------
The patch looks correct to me. Some minor comments:
In lessThanString() the following is changed:
- if (pattern.length() == 0)
+ if (pattern == null)
{
- // pattern is ""
return null;
}
Couldn't the entire if be removed? If pattern could be null, we would have got
a NullPointerException here with the old code, so I don't think it ever will be
null.
Some comments should be updated:
- javadoc for lessThanString says: (NOTE: This may be null if the pattern is
an empty string.)
- a comment in lessThanString says:
/* Find the last non-wildcard character in the pattern
* and increment it. In the most common case,
* "asdf%" becomes "asdg". However, we need to
* handle the following:
*
* pattern return
* ------- ------
* "" null
* "%..." SUPER_STRING (match against
super string)
* "_..." SUPER_STRING (match against
super string)
* "asdf%" "asdg"
*/
-> null should be replaced with SUPER_STRING
- this comment in lessThanString should also be changed:
// Pattern starts with wildcard.
if (upperLimit.length() == 0) {
return SUPER_STRING;
}
-- > Should say "Pattern is empty or starts with wildcard."
> LIKE does not match empty strings when used with a prepared statement
> ---------------------------------------------------------------------
>
> Key: DERBY-1231
> URL: http://issues.apache.org/jira/browse/DERBY-1231
> Project: Derby
> Issue Type: Bug
> Components: JDBC, SQL
> Affects Versions: 10.2.1.6, 10.1.2.1, 10.3.0.0, 10.1.3.1
> Reporter: Dyre Tjeldvoll
> Assigned To: Bernt M. Johnsen
> Fix For: 10.2.2.0
>
> Attachments: DERBY-1231.diff, vti.java
>
>
> LIKE should give true for two 0-length strings. See SQL 2003 Ch. 8.5
> General Rules 3)c)i)
> The query SELECT * FROM t WHERE v like ''
> appears to give me all rows where v is an empty
> string, as expected.
> But a prepared statement
> SELECT * FROM t WHERE v like ?, with setString(1, "")
> always returns an empty result set. See attached repro for the full example.
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