probe7.py

#!/usr/bin/env python3
"""probe7.py - pin down how a relation names its schema.

`relations()` resolves a relation's schema with `namespaces[parent - 32]`. That
rule was inferred from four data points across two files, and the base of 32 is
a magic constant. It is the last guess left in the read path.

Three databases, each designed to break a different explanation:

  many      eight schemas, relations in each, created in a known order
  gaps      schemas created then dropped, so array position and creation
            order come apart
  reorder   schemas created in an order whose names sort differently, to
            separate "index in the array" from "alphabetical rank"

For each, dump every namespace's oid and array position next to the `parent` of
every relation, and check the candidate rules against the truth the API reports.
"""
import os
import shutil
import sys

from tableauhyperapi import (HyperProcess, Connection, Telemetry, CreateMode,
                             TableDefinition, SqlType, NULLABLE, TableName)

HERE = os.path.dirname(os.path.abspath(__file__))
OUT = os.path.join(HERE, "probes7")


def make(hp, name, schemas, drop=()):
    """Create `schemas` in order, drop those in `drop`, one table per survivor."""
    path = os.path.join(OUT, f"{name}.hyper")
    with Connection(hp.endpoint, path, CreateMode.CREATE_AND_REPLACE) as c:
        for s in schemas:
            c.catalog.create_schema(s)
        for s in drop:
            c.execute_command(f'DROP SCHEMA "{s}" CASCADE')
        for s in schemas:
            if s in drop:
                continue
            tdef = TableDefinition(TableName(s, f"t_{s}"), [
                TableDefinition.Column("v", SqlType.int(), NULLABLE)])
            c.catalog.create_table(tdef)
            c.execute_command(f'INSERT INTO {tdef.table_name} VALUES (1),(2),(3)')
    return path


def main():
    shutil.rmtree(OUT, ignore_errors=True)
    os.makedirs(OUT)
    with HyperProcess(telemetry=Telemetry.DO_NOT_SEND_USAGE_DATA_TO_TABLEAU) as hp:
        make(hp, "many", [f"s{i}" for i in range(8)])
        # create ten, drop four: array position no longer tracks creation order
        make(hp, "gaps", [f"g{i}" for i in range(10)],
             drop=["g1", "g3", "g4", "g7"])
        # creation order is the reverse of alphabetical order
        make(hp, "reorder", ["zeta", "yankee", "xray", "whiskey", "victor"])
    print(f"wrote 3 databases to {OUT}")
    return 0


if __name__ == "__main__":
    sys.exit(main())