Postgres-XC - pgxc_ddl
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This directory contains pgxc_ddl, an application used to make a cold synchronization of DDL
in a Postgres-XC cluster by launching DDL and then copy Coordinator catalog file
data from a remote Coordinator (where DDL has been launched) to other Coordinators.

pgxc_ddl can also be used to synchronize catalog files.

pgxc_ddl was put in the default install repository before DDL synchronizing was implemented
(prior to version Postgres-XC 0.9.3).

pgxc_ddl can be used with a configuration file called pgxc.conf.
This file is kept with the name pgxc.conf.sample to stick with PostgreSQL format.
Up to v0.9.3, pgxc.conf was by default installed by initdb in a data folder,
but this is not really necessary since DDL Synchronization is implemented in Postgres-XC.

So it is kept in a separate repository src/pgxc/bin/pgxc_ddl/.

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pgxc_ddl
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This script uses the following options:
- D to locate the data folder, necessary to find pgxc.conf,
  containing the characteristics of all the coordinators
- l to locate the folder where applications are
- f for a DDL file used as input
- d for a Database name on which to launch DDL
- n coordinator number where to launch DDL,
  number based on the one written in pgxc.conf
- t base name of folder where to save configuration files,
  by default /tmp/pgxc_config, completed by $$ (process number for folder name uniqueness)

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pgxc.conf.sample
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Same format as for GUC files is used.

This configuration file contains the list of following parameters:
- coordinator_hosts, list of Coordinator hosts
  This is an array and format is 'host_name_1,host_name_2'.
- coordinator_ports, list of Coordinator ports
  This is an array and format is 'port_1,port_2'
- coordinator_folders
  This is an array and format is 'data_folder_1,data_folder_2'

All the arrays need to have the same size equal to the number of Coordinators.