clone_schema is a PostgreSQL utility that makes a copy of a given schema (DDL and/or DATA). It is based on the Community version of PostgreSQL. It works on most Linux distros and Windows versions. It also runs on PostgreSQL in the cloud (AWS, GCP, MS Azure).
Handles following objects:
- Tables - structure (UDT columns, indexes, constraints, keys) and optionally, data
- Views, Materialized Views - Structure and data
- Sequences, Serial, Identity
- Functions/Procedures
- Types (composite and enum)
- Collations, Domains, Rules, Policies
- Triggers, Trigger Functions
- Comments
- ACLs (Permissions/Grants)
Arguments:
- source schema
- target schema
- Enumerated list
Returns: INTEGER (0 for success, positive non-zero number for an error)
source schema Required: text - schema name
target schema Required: text - table name
ENUM list Required: One of 'DATA','NODATA','DDLONLY'
ENUM list Optional: 'NOOWNER','NOACL','VERBOSE','FILECOPY'
By default, ownership and privileges are also cloned from source to target schema. To override, specify NOOWNER and/or NOACL (similar to how pg_dump works). When NOOWNER is specified, the one running the script is the default owner unless overridden by a SET ROLE command before running this script. You may get faster results copying data to/from disk instead of in-memory copy. FILECOPY is a workaround for tables with complex UDT-type columns that fail to copy. It only works for On-Prem PG Instances since it relies on using the COPY command to write to and read from disk on which the PostgreSQL server resides.
Sequences, Serial, and Identity
Serial is treated the same way as sequences are with explicit sequence definitions. Although you can create a serial column with the serial keyword, when you export it through pg_dump, it loses its serial definition and looks like a plain sequence. This program also attempts to set the nextval (using setval) for all 3 types which have a valid last_value from the pg_sequences table.
Clone the schema with no data:
select clone_schema('sample', 'sample_clone', 'NODATA');
Clone the schema with data:
select clone_schema('sample', 'sample_clone', 'DATA');
select clone_schema('sample', 'sample_clone', 'DATA','VERBOSE'); -- show row copy progress
Just generate DDL:
select clone_schema('sample', 'sample_clone', 'DDLONLY');
In this case, standard output with "INFO" lines are the generated DDL.
The schema_object_counts.sql file is useful for validating the cloning results. Just run it against source and target schemas to validate object counts after changing default schema name, sample.
Regression Testing is done in the following order:
- Execute the sampledb.sql script to create the clone_testing database and the sample schema within it as the basis for the source schema.
- Clone the sample schema in the 3 ways possible (NODATA, DATA, DDLONLY).
- Run the schema_object_counts.sql queries to compare object counts and rows from the source and target schemas.
- Repeat all of the above for all supported versions of PG.
- Testing and validation is done only through the Community version of PostgreSQL.
- The target schema uses the same tablespace(s) as the source schema.
- Dependent on an integrated function, pg_get_tabledef(), copied from another project, https://github.com/MichaelDBA/pg_get_tabledef.
- Only works for PG Versions 10 and up.
- You should not clone the "public" schema. The resulting output may not be accurate even if it finishes without any errors.
- You should not use multiple, user-defined schema objects and expect cloning one schema to another to work. This project does not support that at the present time. It only supports 3 schemas basically: the source schema, the target schema, and objects defined in the public schema referenced by those user-defined schemas.
- Index and key names are not all the same in the cloned schema since some of the tables are created with the CREATE TABLE ... (LIKE ...) construct. Those index names are automatically fabricated by PG with naming format that is prepended with table and column names separated by underscores and ending with "_idx" or "_key".
- Foreign Tables are not handled at the present time. They must be done manually.
- Although clone_schema supports data copy, it is not very efficient for large datasets. It only copies tables one at a time. Using pg_dump/pg_restore in directory mode using parallel jobs would be a lot more efficient for large datasets.
Sponsor: http://elephas.io/
Compare cloning with EnterpriseDB's version that only works with their Advanced Server: https://www.enterprisedb.com/edb-docs/d/edb-postgres-advanced-server/user-guides/user-guide/11/EDB_Postgres_Advanced_Server_Guide.1.078.html