Re^2: Searching and Coutning using 2 files with multiple columns

Ok. I changed my code to do a Mysql query. I have 2 files DB and a MySQL Table. The mysql table is constructed with 3 column: chrom, start, end. DB has 7 columns. For each line in DB, I want to count the number of times that col2 matches chrom and start is BETWEEN col3 and col4. Then I want to print that value in DB col8. Here is the code I have:

#!/usr/bin/perl

# PERL MODULE
use DBI;

my $DB_NAME = "H3K36me3";
my $DB_USER = "root";
my $DB_PASS = "password";

my $dbh = DBI->connect("DBI:mysql:$DB_NAME","$DB_USER","$DB_PASS");

open (FILE,"@ARGV[0]")||die "usage: perl MySQL.query.pl <DB> ";
@array=<FILE>;
close(FILE);

foreach $line (@array){
    my ($Gene,$chr_id,$left,$right,$Strand,$ExonCount,$SizeKB)=split(/
+\t/,$line);
    $sql = "select count(*) from H3K36me3 where chrom =\"$chr_id\" AND
+ start between $left AND $right";
    $sth= $dbh->prepare($sql);
    @Count=$sth->execute()||die "problem Here!\n";
    @Count=$sth->fetchrow();
    while (@Count = $sth->fetchrow()) {    
        print "@Count[0]\n";
    }
}
[download]

The problem is that I can print it to the screen and it will slowly work (the MySQL table is 20 million rows), but when I go to print to file with ' perl MySQL.query.pl DB > Out.txt' it stops around ~6000 rows. It actually stops in a wierd way, like if the actual count is 30, it will only print 3. How do I deal with this?

Comment on Re^2: Searching and Coutning using 2 files with multiple columns Download Code

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Re^3: Searching and Coutning using 2 files with multiple columns by moritz (Cardinal) on Feb 19, 2010 at 16:56 UTC
There are lots of ways in which you can improve your code. The first is to tell mysql to build indexes on the `chrom` and the `start` columns. The second is to use prepared statements and `execute()` as show in the DBI documentation and in this tutorial. If you use the `RaiseError` option in `DBI->connect`, you can leave out the `\|\|die` and get much better error messages. It actually stops in a wierd way, like if the actual count is 30, it will only print 3. How do I deal with this? How does it "stop"? Does it hang? or does it terminate? What is the exit code? does it run out of memory or disk space? Perl 6 - links to (nearly) everything that is Perl 6.	[reply] [d/l] [select]
Re^4: Searching and Coutning using 2 files with multiple columns by shart3 (Novice) on Feb 19, 2010 at 17:52 UTC
It would just hang. It ended up running all night. The processor was still processing, but I wasn't getting any data out. I will try to index my MySQL table to make it run faster. I have to learn how to do it, but for now I am doing `mysql> create index Chr_start_end using btree on H3K36me3 (chrom,start,end)` Thanks for the suggestion!	[reply] [d/l]
Re^4: Searching and Coutning using 2 files with multiple columns by shart3 (Novice) on Feb 19, 2010 at 18:08 UTC
Building the index worked! Thanks again!	[reply]


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