[Bug]: Schema introspection fails on PostgreSQL < 11 (column "prokind" does not exist)

[earmellin]

Describe the bug

Description

Connecting to a PostgreSQL 9.6 server fails because the schema/routine
introspection query references pg_proc.prokind. That column was introduced
in PostgreSQL 11; on 9.x and 10 it does not exist, so the query errors out
with SQLSTATE 42703.

The same incompatibility historically hit phpPgAdmin, jOOQ, EF Core Power Tools,
etc. when PG 11 changed pg_proc: the boolean columns proisagg and
proiswindow were collapsed into the single prokind char column.

Environment

• Tabularis version: 0.13.3
• OS: macOS 26.5.1
• PostgreSQL server: 9.6

Actual behavior

ERROR: column "prokind" does not exist
SQLSTATE: 42703
HINT: Perhaps you meant to reference the column "pg_proc.probin".
file: parse_relation.c, routine: errorMissingColumn

Expected behavior

The connection opens and the schema tree loads on PostgreSQL 9.6 and 10,
the same way it does on 11+.

Root cause & suggested fix

Make the routine-introspection query version-aware. Branch on the server
version (e.g. SHOW server_version_num / current_setting('server_version_num')::int):

• PG >= 110000 → keep using prokind.
• PG < 110000 → derive an equivalent value from the old columns, e.g.:

  CASE
    WHEN p.proisagg    THEN 'a'   -- aggregate
    WHEN p.proiswindow THEN 'w'   -- window
    ELSE 'f'                      -- normal function
  END AS prokind

(Procedures — prokind = 'p' — don't exist before PG 11, so f/a/w
fully cover the pre-11 cases.)

Same treatment is needed for any other catalog query that assumes prokind.

To Reproduce

1. Add a connection to a PostgreSQL 9.6 server.
2. Connect (the failure happens while building the object tree / listing
   stored routines).

OS Version

macos 26.5.1

Tabularis Version

v0.13.3

Relevant Log Output

[debba]

Hi @earmellin ,
are you able to create a PR for it?

[earmellin]

@debba done

[debba]

Too fast :) @earmellin