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From "Knut Anders Hatlen (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5537) Casting to a shorter string type does not warn about truncation
Date Wed, 14 Dec 2011 10:43:36 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5537?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13169254#comment-13169254
] 

Knut Anders Hatlen commented on DERBY-5537:
-------------------------------------------

SQLChar.java has this comment:

            /*
            ** Check whether any non-blank characters will be truncated.
            */
            if (errorOnTrunc)
                hasNonBlankChars(getString(), desiredWidth, sourceWidth);
            //RESOLVE: should issue a warning instead

Similar in SQLBit.java:

			if (errorOnTrunc)
			{
				// error if truncating non pad characters.
				for (int i = desiredWidth; i < dataValue.length; i++) {

					if (dataValue[i] != SQLBinary.PAD)
						throw StandardException.newException(SQLState.LANG_STRING_TRUNCATION, getTypeName(),

									StringUtil.formatForPrint(this.toString()),
									String.valueOf(desiredWidth));
				}
			}
			//else
			//{
			// RESOLVE: when we have warnings, issue a warning if
			// truncation of non-zero bits will occur
			//}

One thing to note is that SQLBit is silent about the truncation, also in the cases where truncation
should cause an exception, if all the truncated bytes are equal to SQLBinary.PAD (0x20). According
to 6.12 <cast specification>, general rule 12, we should always generate a warning on
truncation of binary string types. For character string types, on the other hand, it is correct
not to warn if all the truncated characters are <space>s.
                
> Casting to a shorter string type does not warn about truncation
> ---------------------------------------------------------------
>
>                 Key: DERBY-5537
>                 URL: https://issues.apache.org/jira/browse/DERBY-5537
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.8.2.2
>            Reporter: Knut Anders Hatlen
>
> SQL:2003, part 2, 6.12 <cast specification> specifies that a truncation warning
should be raised when casting from one (character or binary) string data type to another.
Derby does truncate, but it doesn't raise a warning:
> ij> values cast('abc' as char(2));
> 1 
> --
> ab
> 1 row selected
> ij> values cast(x'cafebabe' as char(2) for bit data);
> 1   
> ----
> cafe
> 1 row selected
> We should generate a warning in order to be compliant.

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