Shantanu's Blog

Corporate Consultant

May 27, 2013

 

python FAQ

How can I import a string file into a list of lists?

import csv

with open(r'example board.txt') as f:
    reader = csv.reader(f, delimiter='\t')
    lines = list(reader)

print lines

http://stackoverflow.com/questions/16705496/how-can-i-import-a-string-file-into-a-list-of-lists/16705512#16705512
_____

save all the text file names from current directory to a file

import glob
file_list = glob.glob('*.txt')
out_file=open('out_file.txt', 'w')
out_file.writelines('\n'.join(i for i in file_list))

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May 24, 2013

 

Infobright not just another Data warehouse

Infobright is a commercial provider of column-oriented relational database software with a focus in machine-generated data. It is tightly integreated with MySQL and hence can be called "DBA friendly".

The community version does not allow DML queries like insert / update and delete. The only way to import data is to use load data command. The errors due to invalid data can be ignored as shown:

mysql>  load data infile '/mnt/data/may03/kham.txt' into table ticket fields terminated by '|';
ERROR 2 (HY000): Wrong data or column definition. Row: 3216228, field: 22.

mysql> set @BH_REJECT_FILE_PATH = '/tmp/reject_file';
Query OK, 0 rows affected (0.04 sec)

mysql> set @BH_ABORT_ON_COUNT = 10;
Query OK, 0 rows affected (0.00 sec)

mysql>  load data infile '/mnt/data/may03/kham.txt' into table ticket fields terminated by '|';
Query OK, 3216227 rows affected, 1 warning (6 min 8.75 sec)
Records: 3216227  Deleted: 0  Skipped: 0  Warnings: 1

mysql> show warnings;
+---------+------+------------------------------+
| Level   | Code | Message                      |
+---------+------+------------------------------+
| Warning | 1105 | 1 rows rejected during load. |
+---------+------+------------------------------+

If you want to check the data via select before committing, then set AUTOCOMMIT to off:

Set AUTOCOMMIT=0;

New data can be seen by the loading session even though its not committed. Complete the load using an explicit COMMIT:

COMMIT;
 

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May 12, 2013

 

Meta Data Locking

How do I know which connection is holding on to the lock?

Identifying what user and thread are holding on to a meta data lock that is preventing other queries from running is not easily traceable. In some cases, a "stale" transaction holds a row lock.

mysql> select trx_mysql_thread_id, trx_started from information_schema.innodb_trx where trx_rows_locked > 0 and trx_query IS NULL order by trx_started;
+---------------------+---------------------+
| trx_mysql_thread_id | trx_started |
+---------------------+---------------------+
| 1 | 2012-06-15 13:48:20 |
| 5 | 2012-06-15 13:58:26 |
+---------------------+---------------------+

mysql> select now() - trx_started as active_period, trx_mysql_thread_id, trx_started from information_schema.innodb_trx where trx_rows_locked > 0 and trx_query IS NULL and (now() - trx_started > 600) order by trx_started;
+---------------+---------------------+---------------------+
| active_period | trx_mysql_thread_id | trx_started |
+---------------+---------------------+---------------------+
| 5689.000000 | 1 | 2012-06-15 13:48:20 |
| 4683.000000 | 5 | 2012-06-15 13:58:26 |
+---------------+---------------------+---------------------+

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