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CONTRIBUTING.md

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What to do ?

There are plenty of postgres features that are not implemted yet.

  1. Head to pg-mem playground
  2. Find some syntax or pg feature that throws an error, but which shouldnt
  3. If it's a parsing exception, add parser unit test in pgsql-ast-parser. Take these ones as reference.
  4. If parsing is OK but the statement you're executing do not behave as expected, add a runner unit test like those ones
  5. Fix unit tests :)

Dont hesitate to create issues to ask questions, guidance or help.

how to implement a new statement

If implementing an unsupported SQL statement may somtimes be hard, it's actually easy to explain how to get started.

A) Implement its parser

pgsql-ast-parser uses Nearley (all .ne files) to build a syntax parser.

  1. Look very hard at the statement syntax (for instance, here is create sequence)
  2. Add the target statement type in pgsql-ast-parser AST based on what I understood.
  3. Implement unit tests I want to pass (ex with create sequence UTs)
  4. Implement its syntax in a new nearley file (example with the create sequence statement) and reference it in main.ne
  5. Work on it until unit tests are all failing, but with an error which is not a parsing error
  6. Add an entry for the new statement in IAstPartialMapper here and add its default visitor implem like here and here until compiler stops screaming
  7. Add the "toSql" implementation of the new statement like here (until compiler stops)
  8. Check that ALL unit tests are green (not only the new ones)
  9. Release pgsql-ast-parser

NB: very seldom the lexer will need to be updated in order to implement the required feature.

B) Executor

  1. install pgsql-ast-parser@latest
  2. Write unit tests (create sequence UTs are here, for instance)
  3. Implement statement... that's the less codified thing, but it starts by adding a new case in this switch for new statements (which should fail to compile with the newly installed pgsql-ast-parser), or fix compilation errors & unit tests for other amendments to the parser.
  4. Check that ALL unit tests are OK
  5. Release 🎉

Some long-term todos:

It does not (yet) support (this is kind-of a todo list):

  • Optimize comma-separated cross-joins by picking join conditions in the where statement & using corresonding indinces (currently enumerating the whole cross-join, which is painful)
  • Gin Indices
  • Cartesian Joins
  • Most of the pg functions are not implemented - ask for them, they're easy to implement !
  • Some aggregations are to be implemented (avg, count, ...) - easy job, but not yet done.
  • Stored procedures
  • Lots of small and not so small things (collate, timezones, tsqueries, custom types ...)
  • Introspection schema (it is faked - i.e. some table exist, but are empty - so Typeorm can inspect an introspect an empty db & create tables)
  • Concurrent transaction commit
  • Collation (see #collation tag in code if you want to implement it)