Re: [jira] Commented: (DERBY-1516) Inconsistent behavior for getBytes and getSubString for embedded versus network

[Lance J. Andersen]

Craig Russell (JIRA) wrote: [ http://issues.apache.org/jira/browse/DERBY-1516?page=comments#action_12424673 ] Craig Russell commented on DERBY-1516: -------------------------------------- Including the discussion from the alias referenced immediately above: One interesting test with 0 length is the case for getSubString(1,0) for a zero length lob. Should it throw an exception or return a zero length string? The API working doesn't give much help to resolve this; the wording for the exception in JDK 1.6 is Throws: SQLException - if there is an error accessing the CLOB value which I guess is equivalent to YMMV... A case for Lance? Even if this case is allowed, should it make a difference if position is > (length+1), e.g. getSubString(2,0) for an empty CLOB? Lance has not replied to a request to update the wording, and I think time is running out on this to be added to the specification in progress. Actually that is not true, i did reply if you check the archives, but this issue is not on my radar as i have other issues that are of higher importance right now given my short window of opportunity due to the Mustang schedule. The jdbc spec has followed the java.lang.String spec pretty closely, modulo 1-origin vs. 0-origin indexing. The String spec allows accessing substrings of a 0-length string, as follows: public String substring(int beginIndex, int endIndex) Returns a new string that is a substring of this string. The substring begins at the specified beginIndex and extends to the character at index endIndex - 1. Thus the length of the substring is endIndex-beginIndex... IndexOutOfBoundsException - if the beginIndex is negative, or endIndex is larger than the length of this String object, or beginIndex is larger than endIndex. For a zero-length String: 1. endIndex must be 0 or else endIndex would be larger than the length of the String; 2. beginIndex must be 0 or else beginIndex would be larger than endIndex. Translating this to jdbc, for a zero-length Clob: 1. position must be 1; 2. length must be 0. I agree we should add positive test cases to extract a zero-length substring from a Clob and Blob. I propose adding to clobTest2 and blobTest2 a test like: blobclob4BLOB.printInterval(clob, 1, 0, 7, i, clobLength) // zero length blobclob4BLOB.printInterval(blob, 1, 0, 7, i, blobLength) // zero length Inconsistent behavior for getBytes and getSubString for embedded versus network ------------------------------------------------------------------------------- Key: DERBY-1516 URL: http://issues.apache.org/jira/browse/DERBY-1516 Project: Derby Issue Type: Bug Components: JDBC Reporter: Craig Russell Assigned To: Craig Russell Priority: Minor Attachments: DERBY-1516.patch, DERBY-1516.patch, DERBY-1516.patch org.apache.derby.client.am.Clob.getSubString(pos, length) and org.apache.derby.client.am.Blob.getBytes(pos, length) check the length for less than zero. if ((pos <= 0) || (length < 0)) { throw new SqlException(agent_.logWriter_, "Invalid position " + pos + " or length " + length); But org.apache.derby.impl.jdbc.EmbedClob(pos, length) and org.apache.derby.impl.jdbc.EmbedBlob(pos, length) check the length for less than or equal to zero. if (length <= 0) throw Util.generateCsSQLException( SQLState.BLOB_NONPOSITIVE_LENGTH, new Integer(length)); The specification does not disallow length of zero, so zero length should be allowed. I believe that the implementation in org.apache.derby.client.am is correct, and the implementation in org.apache.derby.impl.jdbc is incorrect.