Migrating Data to FlexusRDS for PostgreSQL Using psql

Preparing for Data Migration

You can access your FlexusRDS for PostgreSQL DB instance through an EIP or from a FlexusX instance.

1. Prepare a FlexusX instance for accessing your FlexusRDS for PostgreSQL DB instance or prepare a device for accessing your FlexusRDS for PostgreSQL DB instance through an EIP.

   To connect to a FlexusRDS for PostgreSQL instance through an EIP, bind an EIP to the instance.

2. Install a PostgreSQL client of the same version as your FlexusRDS for PostgreSQL instance on the prepared FlexusX instance or device.
   

   A PostgreSQL database or client comes with pg_dump and psql.

Exporting Data

Before migrating an existing PostgreSQL database to FlexusRDS for PostgreSQL, you need to export data first.

• The export tool must match the DB engine version.
• Database migration is performed offline. Before the migration, you must stop any applications using the source database.

1. Log in to the FlexusX instance or device that can access the FlexusRDS for PostgreSQL instance.
2. Use the pg_dump tool to export the source database into an SQL file.

   pg_dump--username=<DB_USER> --host=<DB_ADDRESS> --port=<DB_PORT> --format=plain --file=<BACKUP_FILE><DB_NAME>

   • DB_USER indicates the database username.
   • DB_ADDRESS indicates the database address.
   • DB_PORT indicates the database port.
   • BACKUP_FILE indicates the name of the file to which the data will be exported.
   • DB_NAME indicates the name of the database to be migrated.

   Enter the database password as prompted.

   

   If the exported SQL file uses INSERT statements, you can easily edit and modify the file. However, the speed of importing data may be slower than that of using COPY statements. You are advised to select a right statement format as needed.

   • If both the source and destination databases are PostgreSQL databases, you are advised to export COPY statements (default). For details, see Example 1: Exporting the source database to an SQL file (COPY).
   • If either of the source and destination databases is a non-PostgreSQL database, you are advised to export INSERT statements. For details, see Example 2: Exporting the source database to an SQL file (INSERT).

   For more information, see pg_dump options.

   Examples:

   • Example 1: Exporting the source database to an SQL file (COPY)

     $ pg_dump --username=root --host=192.168.151.18 --port=5432 --format=plain --file=backup.sql my_db

     Password for user root:

   • Example 2: Exporting the source database to an SQL file (INSERT)

     $ pg_dump --username=root --host=192.168.151.18 --port=5432 --format=plain --inserts --file=backup.sql my_db

     Password for user root:

   • Example 3: Exporting all table structures from the source database to an SQL file

     $ pg_dump --username=root --host=192.168.151.18 --port=5432 --format=plain --schema-only --file=backup.sql my_db

     Password for user root:

   • Example 4: Exporting all table data from the source database to an SQL file

     $ pg_dump --username=root --host=192.168.151.18 --port=5432 --format=plain --data-only --file=backup.sql my_db

     Password for user root:

   After the commands in any of the above examples are executed, a backup.sql file will be generated as follows:

   [rds@localhost ~]$ ll backup.sql
   -rw-r-----. 1 rds rds 2714 Sep 21 08:23 backup.sql

3. Use pg_dump to export tables from the source database to an SQL file.

   pg_dump --username=<DB_USER> --host=<DB_ADDRESS> --port=<DB_PORT> --format=plain --file=<BACKUP_FILE> <DB_NAME> --table=<TABLE_NAME>

   • DB_USER indicates the database username.
   • DB_ADDRESS indicates the database address.
   • DB_PORT indicates the database port.
   • BACKUP_FILE indicates the name of the file to which the data will be exported.
   • DB_NAME indicates the name of the database to be migrated.
   • TABLE_NAME indicates the name of the specified table in the database to be migrated.

   Enter the database password as prompted.

   Examples:

   • Example 1: Exporting one table from the source database to an SQL file

     $ pg_dump --username=root --host=192.168.151.18 --port=5432 --format=plain --file=backup.sql my_db --table=test

     Password for user root:

   • Example 2: Exporting multiple tables from the source database to an SQL file

     $ pg_dump --username=root --host=192.168.151.18 --port=5432 --format=plain --file=backup.sql my_db --table=test1 --table=test2

     Password for user root:

   • Example 3: Exporting all tables starting with ts_ from the source database to an SQL file

     $ pg_dump --username=root --host=192.168.151.18 --port=5432 --format=plain --file=backup.sql my_db --table=ts_*

     Password for user root:

   • Example 4: Exporting all tables except those starting with ts_ from the source database to an SQL file

     $ pg_dump --username=root --host=192.168.151.18 --port=5432 --format=plain --file=backup.sql my_db -T=ts_*

     Password for user root:

   After the commands in any of the above examples are executed, a backup.sql file will be generated as follows:

   [rds@localhost ~]$ ll backup.sql
   -rw-r-----. 1 rds rds 2714 Sep 21 08:23 backup.sql

Importing Data

1. Log in to the FlexusX instance or device that can access the FlexusRDS for PostgreSQL instance.
2. Ensure that the destination database to which data is to be imported exists.

   If the destination database does not exist, run the following command to create a database:

   # psql --host=<DB_ADDRESS>--port=<DB_PORT>--username=root--dbname=postgres-c "create database<DB_NAME>;"

   • DB_ADDRESS indicates the IP address of the DB instance.
   • DB_PORT indicates the database port of the DB instance.
   • DB_NAME indicates the name of the database to which data is to be imported.

3. Import the exported file to FlexusRDS for PostgreSQL.

   # psql --host=<DB_ADDRESS> --port=<DB_PORT>--username=root--dbname=<DB_NAME>--file=<BACKUP_DIR>/backup.sql

   • DB_ADDRESS indicates the IP address of the DB instance.
   • DB_PORT indicates the database port of the DB instance.
   • DB_NAME indicates the name of the database to which data is to be imported. Ensure that the database exists.
   • BACKUP_DIR indicates the directory where the backup.sql file is stored.

   Enter the password for the DB instance when prompted.

   Example:

   # psql --host=172.16.66.198 --port=5432 --username=root --dbname=my_db --file=backup.sql

   Password for user root:

4. View the import result.

   my_db=> \l my_db

   In this example, the database named my_db has been imported.

   my_db=> \l my_db
   List of databases
   Name  | Owner | Encoding | Collate     | Ctype       | Access privileges
   ------+-------+----------+-------------+-------------+-----------
   my_db | root  | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
   (1 row)