You would need to modify the modules to be more efficient with memory usage with huge tables. You could either modify Tie::RDBM to use the Pg module for direct PostgreSQL access with cursors. Or modify DBD::Pg to use cursors. Otherwise, the SELECT statement to fetch the keys stores all the data on the client. You might want to investiage MySQL and see if DBD::Mysql uses cursors. It also looks like you will have to modify Tie::RDBM to not cache the values that it fetches.

The important question to ask is whether you really need a tied hash. If you don't need one, then you can do operations more efficiently with custom database accesses. Since PostgreSQL doesn't use cursors, you will have to avoid any queries that return all the keys.

For example, counting the number of keys is doable with a SELECT COUNT(*) FROM table statement. You might want to normalize the database to store each value in a row of a second table. Then you won't need to use Perl serialization to store the data structures. You can the total number of values with SELECT COUNT(*) FROM values. And individual counts for each key: SELECT COUNT(*) FROM values WHERE key = $key.

In reply to Re: Re: Re: iteration through tied hash eat my memory by iburrell
in thread iteration through tied hash eat my memory by ph0enix

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.