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Top Forums Shell Programming and Scripting script to merge two files on an index Post 302639917 by LMHmedchem on Sunday 13th of May 2012 04:33:58 PM
Old 05-13-2012
Thanks for the post. One of the issues I am looking at here is that I use things like this fairly often, but the formats of the files can be very different. They could have hundreds of columns and the header name and location of the index column can vary quire a bit. In most cases, it is easier to use a header name to specify the index column and it's harder to use a simple tokenizer where the number of columns and location of the index is not constant. I am trying to get away from scripts with significant hard coding that needs to be changed.

In c++, I might create a hash table using the index value of the second file ask the key and the remainder of the row as the value. I would read in the second file and store it on the index value and then loop through the first file looking up the file 2 data that goes with each file 1 row. This would also mean that the files wouldn't have to be in the same order. That wouldn't be super fast, but processing files with 150,000+ rows will take some time no matter what the method. I don't really know how to do that sort of thing in a scripting language.

I don't think that something of that sophistication is really necessary, if the rows are not in the same order, another script could be used to sort them. I think that all that is really necessary is to check that the number of rows is the same and then test each row for matching key values, but I would like to have a script that will just take arguments for the filenames and index header name and have the rest work for pretty much any pair of files.

LMHmedchem
 

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Alzabo::Runtime::Index(3pm)				User Contributed Perl Documentation			       Alzabo::Runtime::Index(3pm)

NAME
Alzabo::Runtime::Index - Index objects SYNOPSIS
use Alzabo::Runtime::Index; DESCRIPTION
This object represents an index on a table. Indexes consist of columns and optional prefixes for each column. The prefix specifies how many characters of the columns should be indexes (the first X chars). Some RDBMS's do not have a concept of index prefixes. Not all col- umn types are likely to allow prefixes though this depends on the RDBMS. The order of the columns is significant. INHERITS FROM
"Alzabo::Index" Note: all relevant documentation from the superclass has been merged into this document. METHODS
columns Returns an ordered list of the "Alzabo::Runtime::Column" objects that are being indexed. prefix ("Alzabo::Runtime::Column" object) A column prefix is, to the best of my knowledge, a MySQL specific concept, and as such cannot be set when using an RDBMSRules module for a different RDBMS. However, it is important enough for MySQL to have the functionality be present. It allows you to specify that the index should only look at a certain portion of a field (the first N characters). This prefix is required to index any sort of BLOB column in MySQL. This method returns the prefix for the column in the index. If there is no prefix for this column in the index, then it returns undef. unique Returns a boolean value indicating whether the index is a unique index. fulltext Returns a boolean value indicating whether the index is a fulltext index. function For function indexes, this returns the function being indexed. id The id is generated from the table, column and prefix information for the index. This is useful as a canonical name for a hash key, for example. Returns a string that is the id which uniquely identifies the index in this schema. table Returns the "Alzabo::Runtime::Table" object to which the index belongs. AUTHOR
Dave Rolsky, <autarch@urth.org> perl v5.8.8 2007-12-23 Alzabo::Runtime::Index(3pm)
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