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clone_schema

clone_schema is a PostgreSQL tool for making a copy of a schema. It includes all objects associated with a schema.

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) <br/>

Arguments:

• source schema <pre>Required: text - schema name</pre>
• target schema <pre>Required: text - table name</pre>
• action <pre>Required: One of 'DATA','NODATA','DDLONLY'</pre>
• Enumerated list <pre>Optional: 'NOOWNER','NOACL','VERBOSE','FILECOPY'</pre>

Returns: INTEGER (0 for success, positive non-zero number for an error) <br/><br/>

Examples<br/> Clone the schema with no data: <br/>

select clone_schema('sample', 'sample_clone', 'NODATA');

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Clone the schema with data: <br/>

select clone_schema('sample', 'sample_clone', 'DATA');<br/> select clone_schema('sample', 'sample_clone', 'DATA','VERBOSE'); -- verbose mode shows row copy progress

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Just generate DDL: <br/>

select clone_schema('sample', 'sample_clone', 'DDLONLY');

In the generated output for DDLONLY, modify the output as follows:

• remove the lines that start with NOTICE:
• remove any other lines that do not begin with INFO:
• Then, remove the first 7 characters of the these lines that begin with INFO: <br/>

The result should be a clean DDL output. <br/><br/><br/>

Ownership/Privileges<br/> 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. <br/><br/> Copying Data 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. <br/> Although pg_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. <br/><br/> Sequences, Serial, and Identity<br/> 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. <br/><br/>

Regression Testing Overview

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.

Assumptions

• Testing and validation is done only through the Community version of PostgreSQL.
• The target schema uses the same tablespace(s) as the source schema.

Limitations

• 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". In DDLOnly mode, this will cause errors when attempting to make comments on indexes. Follow the NOTE in DDL output for lines you may want to comment out or fix.
• Foreign Tables are not handled at the present time. They must be done manually. <br/>