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http://issues.apache.org/jira/browse/DERBY-1917?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12461669
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V.Narayanan commented on DERBY-1917:
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Thanks for taking a look at this issue and commenting on it.
1) I will change the identation to use tabs instead of spaces and repost my
patch
2) Would'nt changing the new lines to use 4 spaces make those lines stand out
from sorrounding code?
3) The position method was earlier being tested for search strings of length
only within 256 as a workaround in BlobClob4BlobTest (That is the only
place in my knowledge that carries a test for the position method). Now it
has been changed to test for arbitary length strings.
4) But as a specific test for this bug I can add the repro attached with this
issue as a test case. Since the chunk size is 256 I could probably add test
cases to test for a range of chunk sizes like 0-256, 256-512.... But IMHO
the existing test case and the repro(if required) should be good enough.
5) From my knowledge of tracing this algorithm it would work irrespective of
the number 256
6) I however do not know if 256 is something like a most efficient chunk size.
I mean the algorithm works most efficiently if your chunk size is 256. I
have not tested this.
thanx once again for the comments and guidance,
Narayanan
> Clob.position fails with Embedded driver and large Clobs
> --------------------------------------------------------
>
> Key: DERBY-1917
> URL: http://issues.apache.org/jira/browse/DERBY-1917
> Project: Derby
> Issue Type: Bug
> Components: JDBC
> Reporter: Fernanda Pizzorno
> Assigned To: V.Narayanan
> Priority: Minor
> Attachments: Position_patch_explanation.txt, position_patch_v1.diff,
> position_patch_v1.stat
>
>
> The method Clob.position(String searchstr, long start) fails when used on
> large lobs if the searchstr is bigger than 256 characters. I have seen two
> different errors, if the search string it bigger than 256 character it is not
> found and if the search string is bigger than 512 characters an exception is
> thrown.
> /* Repro */
> // Connect
> Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
> Connection conn =
> DriverManager.getConnection("jdbc:derby:ReproClob;create=true", "app", "app");
>
> // Create table and populate
> Statement stmt = conn.createStatement();
> try {
> stmt.executeUpdate("DROP TABLE tmpClob");
> } catch (SQLException se) {}
> stmt.executeUpdate("CREATE TABLE tmpClob (a int, b clob(40K))");
>
> PreparedStatement ps = conn.prepareStatement("INSERT INTO tmpClob
> VALUES (?, ?)");
> String tmp = "abcdefghijklmnopqrstuvxyz";
> StringBuilder sb = new StringBuilder();
> for (int i=0; i<1500; i++) {
> sb.append(tmp);
> }
> ps.setInt(1, 1);
> ps.setString(2, sb.toString());
> ps.executeUpdate();
> ps.close();
> ResultSet rs = stmt.executeQuery("SELECT * FROM tmpClob");
> if (rs.next()) {
> Clob c = rs.getClob(2);
> // Bug #1
> String subString1 = c.getSubString(100, 513);
> try {
> long i1 = c.position(subString1, 90);
> System.out.println("Found searched string at: " + i1);
> } catch (SQLException se) {
> System.out.println("FAILURE REPRODUCED:
> Clob.position(string, int) throws an exception when the length of the search
> string is bigger than 512");
> se.printStackTrace();
> while (se != null) {
> System.out.println("FAIL: " + se.getMessage());
> se = se.getNextException();
> }
> }
> // Bug #2
> String subString2 = c.getSubString(100, 257);
> long i2 = c.position(subString2, 90);
> if (i2 == -1) {
> System.out.println("FAILURE REPRODUCED:
> Clob.position(string, int) does not find the search string if its length is
> bigger than 256");
> } else {
> System.out.println("Found searched string at: " + i2);
> }
> }
> rs.close();
> stmt.close();
> conn.rollback();
> conn.close();
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