pg_readme 0.5.2

This Release
pg_readme 0.5.2
Date
Status
Stable
Latest Stable
pg_readme 0.5.6 —
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Abstract
Generates a Markdown README from COMMENT objects found in the pg_description system catalog.
Description
The pg_readme PostgreSQL extension provides functions to generate a README.md document for a database extension or schema, based on COMMENT objects found in the pg_description system catalog.
Released By
bigsmoke
License
GPL 3
Resources
Special Files
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Extensions

pg_readme 0.5.2

Documentation

LICENSE
LICENSE

README


pg_extension_name: pg_readme pg_extension_version: 0.5.2 pg_readme_generated_at: 2023-01-24 14:23:52.913741+00

pg_readme_version: 0.5.2

The pg_readme PostgreSQL extension

The pg_readme PostgreSQL extension provides functions to generate a README.md document for a database extension or schema, based on COMMENT objects found in the pg_description system catalog.

Usage

To use pg_readme in your extension, the most self-documenting way to do it is to create a function that calls the readme.pg_extension_readme(name) function. Here is an example take from the pg_rowalesce extension:

sql create function pg_rowalesce_readme() returns text volatile set search_path from current set pg_readme.include_view_definitions to 'true' set pg_readme.include_routine_definition_like to '{test__%}' language plpgsql as $plpgsql$ declare _readme text; begin create extension if not exists pg_readme with version '0.1.0'; _readme := pg_extension_readme('pg_rowalesce'::name); raise transaction_rollback; -- to drop extension if we happened to `CREATE EXTENSION` for just this. exception when transaction_rollback then return _readme; end; $plpgsql$;

In the above example, the pg_readme.* settings are (quite redundantly) set to their default values. There is no need to add pg_readme to the list of requirements in your extension's control file; after all, the extension is only intermittently required, by you, when you need to update your extension's README.md.

To make it easy (and self-documenting) to update the readme, add something like the following recipe to the bottom of your extension's Makefile:

sql README.md: README.sql install psql --quiet postgres < $< > $@

And turn the README.sql into something like this (again an example from pg_rowalesce):

```sql \pset tuples_only \pset format unaligned

begin;

create schema rowalesce;

create extension pg_rowalesce with schema rowalesce cascade;

select rowalesce.pg_rowalesce_readme();

rollback; ```

Now you can update your README.md by running:

make README.md

COMMENT (also on your extension), play with it, and never go back. And don't forget to send me the pull requests for you enhancements.

Markdown

The pg_readme author has made the choice for Markdown, not out of love for Markdown, but out of practicality: Markdown, in all its neo-formal interprations, has become ubiquitous. Also, it has a straight-forward fall-through to (X)HTML. And we're not creating tech. books here (where TEI or DocBook would have been the superior choice); we're merely generating online/digital documentation on the basis of inline COMMENTs.

To make the pain of Markdown's many competing extensions and implementations somewhat bearable, pg_readme attempts to stick to those Markdown constructs that are valid both according to:

“Attempts to”, because pg_readme relies heavily on MarkDown tables, which are supported by GFM, but not by CommonMark.

Processing instructions

pg_readme has support for a bunch of special XML processing instructions that you can include in the Markdown COMMENT ON EXTENSION or COMMENT ON SCHEMA objects:

  • <?pg-readme-reference?> will be replaced with a full references with all the objects found by pg_readme that belong to the schema or extension (when pg_schema_readme() or pg_extension_readme() are run respectively.
  • <?pg-readme-colophon?> adds a colophon with information about pg_readme to the text.

The following pseudo-attributes are supported for these processing instructions:

| Pseudo-attribute | Coerced to | Default value | | -------------------------- | ---------- | ------------------------------------ | | context-division-depth | smallint | 1 | | context-division-is-self | boolean | false | | division-title | text | 'Object reference' / 'Colophon' |

(These attributes are called pseudo-attributes, because the XML spec does not prescribe any particular structure for a processing instruction's content.

Extension-specific settings

| Setting | Default | | -------------------------------------------- | --------------------------------------------------------------- | | pg_readme.include_view_definitions | true | | pg_readme.readme_url | 'https://github.com/bigsmoke/pg_readme/blob/master/README.md' | | pg_readme.include_routine_definitions_like | '{test__%}' | | pg_readme.include_this_routine_definition | null |

pg_readme.include_this_routine_definition is meant to be only used on a routine-local level to make sure that the definition for that particular routine is either always or never included in the reference, regardless of the pg_readme.include_routine_definitions_like setting.

For pg_readme version 0.3.0, pg_readme.include_routine_definitions has been deprecated in favor of pg_readme.include_routine_definitions_like, and pg_readme.include_routine_definitions is now interpreted as:

| Legacy setting | Deduced setting | | ----------------------------------------------- | --------------------------------------------------------------- | | pg_readme.include_routine_definitions is null | pg_readme.include_routine_definitions_like = array['test__%'] | | pg_readme.include_routine_definitions = true | pg_readme.include_routine_definitions_like = array['%'] | | pg_readme.include_routine_definitions = false | pg_readme.include_routine_definitions_like = array[]::text[] |

To-dos and to-maybes

Missing features

  • Table synopsis is not generated yet.

Ideas for improvement

  • Support for <?pg-readme-install?> PI could be nice.
  • Support for a <?pg-readme-table-rows?> PI in the COMMENT of specific tables could be a nice addition for extensions/schemas that have type-type tables.
  • Automatically turning references to objects from other/builtin extensions or schemas into links could be a plus. But this might also render the raw markup unreadable. That, at least, would be a good argument against doing the same for extension-local object references.

The origins of the pg_readme extension

pg_readme, together with a decent number of other PostgreSQL extensions, was developed as part of the backend for the super-scalable FlashMQ MQTT SaaS service. Bundling and releasing this code publically has:

  • made the PostgreSQL schema architecture cleaner, with fewer interdependencies;
  • made the documentation more complete and up-to-date;
  • increased the amount of polish; and
  • reduced the number of rough edges.

The public gaze does improve quality!

Object reference

Routines

Function: pg_extension_readme (name)

pg_extension_readme() automatically generates a README.md for the given extension, taking the COMMENT ON EXTENSION as the prelude, and optionally adding a full reference (with neatly layed out object characteristics from the pg_catalog) in the place where a &lt;?pg-readme-reference?&gt; processing instruction is encountered in the `COMMENT ON EXTENSION'.

See the Processing instructions section for details about the processing instructions that are recognized and which pseudo-attributes they support.

Function arguments:

| Arg. # | Arg. mode | Argument name | Argument type | Default expression | | ------ | ---------- | ----------------------------------------------------------------- | -------------------------------------------------------------------- | ------------------- | | $1 | IN | | name | |

Function return type: text

Function attributes: STABLE

Function-local settings:

  • SET search_path TO readme, public, pg_temp

Function: pg_readme_colophon (pg_readme_collection_type, name, smallint, boolean, text)

pg_readme_colophon() is a function internal to pg_readme that is used by pg_readme_pis_process() to replace &lt;?pg-readme-colophon?&gt; processing instructions with a standard colophon indicating that pg_readme was used to generate a schema or extension README.

See the Processing instructions section for an overview of the processing instructions and their pseudo-attributes.

Function arguments:

| Arg. # | Arg. mode | Argument name | Argument type | Default expression | | ------ | ---------- | ----------------------------------------------------------------- | -------------------------------------------------------------------- | ------------------- | | $1 | IN | collection_type$ | pg_readme_collection_type | | | $2 | IN | collection_name$ | name | | | $3 | IN | context_division_depth$ | smallint | 1 | | $4 | IN | context_division_is_self$ | boolean | false | | $5 | IN | division_title$ | text | 'Colophon'::text |

Function return type: text

Function attributes: IMMUTABLE, LEAKPROOF, PARALLEL SAFE

Function: pg_readme_meta_pgxn()

Returns the JSON meta data that has to go into the META.json file needed for PGXN—PostgreSQL Extension Network packages.

The Makefile includes a recipe to allow the developer to: make META.json to refresh the meta file with the function's current output, including the default_version.

Function return type: jsonb

Function attributes: STABLE

Function: pg_readme_object_reference (pg_readme_objects_for_reference, pg_readme_collection_type, name, smallint, boolean, text)

pg_readme_object_reference() is a function internal to pg_readme that is delegated to by pg_readme_pis_process() to replace &lt;?pg-readme-reference?&gt; processing instructions with a standard colophon indicating that pg_readme was used to generate a schema or extension README.

See the Processing instructions section for an overview of the processing instructions and their pseudo-attributes.

Function arguments:

| Arg. # | Arg. mode | Argument name | Argument type | Default expression | | ------ | ---------- | ----------------------------------------------------------------- | -------------------------------------------------------------------- | ------------------- | | $1 | IN | objects$ | pg_readme_objects_for_reference | | | $2 | IN | collection_type$ | pg_readme_collection_type | | | $3 | IN | collection_name$ | name | | | $4 | IN | context_division_depth$ | smallint | 1 | | $5 | IN | context_division_is_self$ | boolean | false | | $6 | IN | division_title$ | text | 'Object reference'::text |

Function return type: text

Function attributes: STABLE

Function-local settings:

  • SET search_path TO readme, public, pg_temp

Function: pg_readme_object_reference__rel_attr_list (pg_class)

Function arguments:

| Arg. # | Arg. mode | Argument name | Argument type | Default expression | | ------ | ---------- | ----------------------------------------------------------------- | -------------------------------------------------------------------- | ------------------- | | $1 | IN | | pg_class | |

Function return type: text

Function attributes: STABLE

Function: pg_readme_pi_pseudo_attrs (text, text)

pg_readme_pi_pseudo_attrs() extracts the pseudo-attributes from the XML processing instruction with the given pi_target$ found in the givenhaystack$ argument.

See the test__pg_readme_pi_pseudo_attrs() procedure source for examples.

Function arguments:

| Arg. # | Arg. mode | Argument name | Argument type | Default expression | | ------ | ---------- | ----------------------------------------------------------------- | -------------------------------------------------------------------- | ------------------- | | $1 | IN | haystack$ | text | | | $2 | IN | pi_target$ | text | |

Function return type: hstore

Function attributes: IMMUTABLE, LEAKPROOF, RETURNS NULL ON NULL INPUT, PARALLEL SAFE

Function: pg_readme_pis_process (text, pg_readme_collection_type, name, pg_readme_objects_for_reference)

pg_readme_object_reference() is a function internal to pg_readme that is responsible for replacing processing instructions in the source text with generated content.

See the Processing instructions section for an overview of the processing instructions and their pseudo-attributes.

Function arguments:

| Arg. # | Arg. mode | Argument name | Argument type | Default expression | | ------ | ---------- | ----------------------------------------------------------------- | -------------------------------------------------------------------- | ------------------- | | $1 | IN | unprocessed$ | text | | | $2 | IN | collection_type$ | pg_readme_collection_type | | | $3 | IN | collection_name$ | name | | | $4 | IN | objects$ | pg_readme_objects_for_reference | |

Function return type: text

Function attributes: STABLE, LEAKPROOF, RETURNS NULL ON NULL INPUT, PARALLEL SAFE

Function-local settings:

  • SET search_path TO readme, public, pg_temp

Function: pg_schema_readme (regnamespace)

pg_schema_readme() automatically generates a README.md for the given schema, taking the COMMENT ON SCHEMA as the prelude, and optionally adding a full reference (with neatly layed out object characteristics from the pg_catalog) in the place where a &lt;?pg-readme-reference?&gt; processing instruction is encountered in the `COMMENT ON SCHEMA'.

See the Processing instructions section for details about the processing instructions that are recognized and which pseudo-attributes they support.

Function arguments:

| Arg. # | Arg. mode | Argument name | Argument type | Default expression | | ------ | ---------- | ----------------------------------------------------------------- | -------------------------------------------------------------------- | ------------------- | | $1 | IN | | regnamespace | |

Function return type: text

Function attributes: STABLE

Function-local settings:

  • SET search_path TO readme, public, pg_temp

Function: string_diff (text, text)

Function arguments:

| Arg. # | Arg. mode | Argument name | Argument type | Default expression | | ------ | ---------- | ----------------------------------------------------------------- | -------------------------------------------------------------------- | ------------------- | | $1 | IN | | text | | | $2 | IN | | text | |

Function return type: text

Function attributes: IMMUTABLE, LEAKPROOF, RETURNS NULL ON NULL INPUT

Procedure: test__pg_readme()

This routine tests the pg_readme extension.

The routine name is compliant with the pg_tst extension. An intentional choice has been made to not depend on the pg_tst extension its test runner or developer-friendly assertions to keep the number of inter-extension dependencies to a minimum.

Procedure-local settings:

  • SET search_path TO readme, public, pg_temp
  • SET pg_readme.include_this_routine_definition TO false
  • SET plpgsql.check_asserts TO true

Procedure: test__pg_readme_pi_pseudo_attrs()

This routine tests the pg_readme_pi_pseudo_attrs() function.

The routine name is compliant with the pg_tst extension. An intentional choice has been made to not depend on the pg_tst extension its test runner or developer-friendly assertions to keep the number of inter-extension dependencies to a minimum.

Procedure-local settings:

  • SET search_path TO readme, public, pg_temp

```sql CREATE OR REPLACE PROCEDURE readme.test__pg_readme_pi_pseudo_attrs() LANGUAGE plpgsql SET search_path TO 'readme', 'public', 'pg_temp' AS $procedure$ begin assert pg_readme_pi_pseudo_attrs( '', 'muizen-stapje' ) = hstore('soort=>woelmuis, hem-of-haar=>piep, a1=>4');

assert pg_readme_pi_pseudo_attrs(
    'Blabla bla <?muizen-stapje soort="woelmuis" hem-of-haar="piep"?> Frotsepots',
    'muizen-stapje'
) = hstore('soort=>woelmuis, hem-of-haar=>piep');

assert pg_readme_pi_pseudo_attrs(
    'Blabla bla <?muizen-stapje ?> Frotsepots',
    'muizen-stapje'
) is null;

end; $procedure$ ```

Types

The following extra types have been defined besides the implicit composite types of the tables and views in this extension.

Composite type: pg_readme_objects_for_reference

sql CREATE TYPE pg_readme_objects_for_reference AS ( table_objects regclass[], view_objects regclass[], procedure_objects regprocedure[], operator_objects regoperator[], type_objects regtype[] );

Domain: pg_readme_collection_type

sql CREATE DOMAIN pg_readme_collection_type AS text CHECK ((VALUE = ANY (ARRAY['extension'::text, 'schema'::text])));

Colophon

This README.md for the pg_readme extension was automatically generated using the pg_readme PostgreSQL extension.