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From "Daniel Dai (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-1443) DefaultTuple underestimate the memory footprint for string
Date Wed, 09 Jun 2010 17:18:13 GMT
DefaultTuple underestimate the memory footprint for string
----------------------------------------------------------

                 Key: PIG-1443
                 URL: https://issues.apache.org/jira/browse/PIG-1443
             Project: Pig
          Issue Type: Bug
          Components: impl
    Affects Versions: 0.7.0
            Reporter: Daniel Dai
            Assignee: Daniel Dai
             Fix For: 0.8.0


Currently, in DefaultTuple, we estimate the memory footprint for string as if it is char array.
The formula we use is:  length * 2 + 12. It turns out we underestimate the memory usage for
string. Here is a list of real memory footprint for string we get from memory dump:

| length of string | memory in bytes |
| 7 | 56 |
| 3 | 48 |
| 1 | 40 |

I did a search and find the following formula can accurately estimate the memory footprint
for string:
{code}
8 * (int) (((length * 2) + 45) / 8) 
{code}

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