The DB, if it is built with SQLite, will be so performant that it is great!

That is a very bold, some would say rash, claim. Given you appear not to understand the problem.

At some point in the run of a program the OP has a hash containing 5000 key/value pairs. At that same point in time on disk, there is a CSV file containing 120,000 lines of 10 fields.

The task is, given the hash and an integer (that represents a field within each record), to produce an output file on disk that contains that subset of the input file where field 1 (0-based) of the record exists as a key in the hash, with the value of the field identified by the number, as its value.

What you are suggesting is that in less than 6 seconds you can:

  1. Build an SQLite DB from the file of 120,000 records.
  2. Perform 5000 SQL queries -- against that 120,000 record DB -- of the form: 
    select * from table where field1 eq ? and field? eq ?;

    [download]
  3. Convert all the results records, from each of the 5000 queries, back to CSV records.
  4. Write them out to the new file.

    (For strict compliance, re-order the retrieved records into input file order before output.)

  5. (Delete the SQLite DB you created!)

Good luck!

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^2: Best way to match a hash with large CSV file by BrowserUk
in thread Best way to match a hash with large CSV file by alphavax

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