dbmerge man page

dbmerge — merge all inputs in sorted order based on the the specified columns

Synopsis

dbmerge --input A.fsdb --input B.fsdb [-T TemporaryDirectory] [-nNrR] column [column...]

or
cat A.fsdb | dbmerge --input - --input B.fsdb [-T TemporaryDirectory] [-nNrR] column [column...]

or
dbmerge [-T TemporaryDirectory] [-nNrR] column [column...] --inputs A.fsdb [B.fsdb ...]

Description

Merge all provided, pre-sorted input files, producing one sorted result. Inputs can both be specified with "--input", or one can come from standard input and the other from "--input". With "--xargs", each line of standard input is a filename for input.

Inputs must have identical schemas (columns, column order, and field separators).

Unlike dbmerge2, dbmerge supports an arbitrary number of input files.

Because this program is intended to merge multiple sources, it does not default to reading from standard input. If you wish to list - as an explicit input source.

Also, because we deal with multiple input files, this module doesn't output anything until it's run.

dbmerge consumes a fixed amount of memory regardless of input size. It therefore buffers output on disk as necessary. (Merging is implemented a series of two-way merges, so disk space is O(number of records).)

dbmerge will merge data in parallel, if possible. The <--parallelism> option can control the degree of parallelism, if desired.

Options

General option:

--xargs
Expect that input filenames are given, one-per-line, on standard input. (In this case, merging can start incrementally.
--removeinputs
Delete the source files after they have been consumed. (Defaults off, leaving the inputs in place.)
-T TmpDir
where to put tmp files. Also uses environment variable TMPDIR, if -T is not specified. Default is /tmp.
--parallelism N
Allow up to N merges to happen in parallel. Default is the number of CPUs in the machine.
--endgame (or --noendgame)
Enable endgame mode, extra parallelism when finishing up. (On by default.)

Sort specification options (can be interspersed with column names):

-r or --descending
sort in reverse order (high to low)
-R or --ascending
sort in normal order (low to high)
-n or --numeric
sort numerically
-N or --lexical
sort lexicographically

This module also supports the standard fsdb options:

-d
Enable debugging output.
-i or --input InputSource
Read from InputSource, typically a file name, or "-" for standard input, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue objects.
-o or --output OutputDestination
Write to OutputDestination, typically a file name, or "-" for standard output, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue objects.
--autorun or --noautorun
By default, programs process automatically, but Fsdb::Filter objects in Perl do not run until you invoke the run() method. The "--(no)autorun" option controls that behavior within Perl.
--help
Show help.
--man
Show full manual.

Sample Usage

Input

File a.fsdb:

#fsdb cid cname
11 numanal
10 pascal

File b.fsdb:

#fsdb cid cname
12 os
13 statistics

These two files are both sorted by "cname", and they have identical schemas.

Command

dbmerge --input a.fsdb --input b.fsdb cname

or

cat a.fsdb | dbmerge --input b.fsdb cname

Output

#fsdb      cid     cname
11 numanal
12 os
10 pascal
13 statistics
#  | dbmerge --input a.fsdb --input b.fsdb cname

See Also

dbmerge2(1), dbsort(1), Fsdb(3)

Referenced By

dbfilecat(1), dbmerge2(1), dbsort(1).

2016-11-30 perl v5.24.0 User Contributed Perl Documentation