Documentation on Postgres Parse tree?

Question

Is there a place that says what that documents the Postgres parse tree? For example from Query Parsing it gives an example of:

   SELECT * FROM foo where bar = 42 ORDER BY id DESC LIMIT 23;
   (
      {SELECT 
      :distinctClause <> 
      :intoClause <> 
      :targetList (
         {RESTARGET 
         :name <> 
         :indirection <> 
         :val 
      ...

But I can't find a place that gives more information, for example, what is indirection in the RESTARGET clause? It does link to the Postgres internals docs @ https://www.postgresql.org/docs/current/overview.html, but I couldn't find anything about the Postgres parse tree in detail from that. Is anything documented on that?

Note: for the question I'm only concerned with the SELECT statement.

@a_horse_with_no_name sure could you share the file(s) then where this is documented? Maybe even an answer with an example of where/how to find what indirection means? — David542
– David542, Commented Dec 12, 2021 at 18:31

Lukas Fittl · Accepted Answer · 2021-12-12 18:41:38Z

1

Most of the relevant structs are defined in parsenodes.h, e.g. ResTarget and its attributes are defined here:

https://github.com/postgres/postgres/blob/master/src/include/nodes/parsenodes.h#L461

You may also find pg_query useful, a library I wrote to parse queries using the Postgres parser: https://github.com/pganalyze/pg_query (the output format is either JSON or Protobuf, and maps to the parsenodes.h struct names 1:1)

answered Dec 12, 2021 at 18:41

Lukas Fittl

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