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From "Thejas M Nair (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (PIG-1821) UDFContext.getUDFProperties does not handle collisions in hashcode of udf classname (+ arg hashcodes)
Date Mon, 02 May 2011 14:37:03 GMT

     [ https://issues.apache.org/jira/browse/PIG-1821?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Thejas M Nair updated PIG-1821:
-------------------------------

    Status: Patch Available  (was: Open)

> UDFContext.getUDFProperties does not handle collisions in hashcode of udf classname (+
arg hashcodes)
> -----------------------------------------------------------------------------------------------------
>
>                 Key: PIG-1821
>                 URL: https://issues.apache.org/jira/browse/PIG-1821
>             Project: Pig
>          Issue Type: Bug
>    Affects Versions: 0.8.0
>            Reporter: Thejas M Nair
>            Assignee: Thejas M Nair
>             Fix For: 0.9.0
>
>         Attachments: PIG-1821.1.patch
>
>
> In code below, if generateKey() returns same value for two udfs, the udfs would end up
sharing the properties object. 
> {code}
> private HashMap<Integer, Properties> udfConfs = new HashMap<Integer, Properties>();
>     public Properties getUDFProperties(Class c) {
>         Integer k = generateKey(c);
>         Properties p = udfConfs.get(k);
>         if (p == null) {
>             p = new Properties();
>             udfConfs.put(k, p);
>         }
>         return p;
>     }
>     private int generateKey(Class c) {
>         return c.getName().hashCode();
>     }
>     public Properties getUDFProperties(Class c, String[] args) {
>         Integer k = generateKey(c, args);
>         Properties p = udfConfs.get(k);
>         if (p == null) {
>             p = new Properties();
>             udfConfs.put(k, p);
>         }
>         return p;
>     }
>     private int generateKey(Class c, String[] args) {
>         int hc = c.getName().hashCode();
>         for (int i = 0; i < args.length; i++) {
>             hc <<= 1;
>             hc ^= args[i].hashCode();
>         }
>         return hc;
>     }
> {code}
> To prevent this, a new class (say X) that can hold the classname and args should be created,
and instead of HashMap<Integer, Properties>,  HashMap<X, Properties> should be
used. Then HahsMap will deal with the collisions. 

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