Properly reflect column attributes: nulllable, autoincrement, comment

[hab6]

Overview

Changes are made to class method IngresDialect::get_columns to provide reflection of column attributes autoincrement and comment and to correctly handle columns that are defined as unique constraints.

The column attributes fix was prompted by failing tests from ComponentReflectionTest::test_get_multi_columns in the SQLAlchemy dialect compliance suite in which the actual reflected results were missing the attributes autoincrement and comment which are part of the expected results.

Notes on Unique Constraints and Null Values

Per Ingres documentation, Ingres tables do not allow columns specified as unique to contains nulls whereas X100 tables do allow columns specified as unique to contain null values.

PostgreSQL doc indicates that column members of unique constraints can be null.

The SQLAlchemy get_multi_columns tests expect that null values are allowed for any column that is part of a unique constraint, and thus with an Ingres database, a number of these tests continue to fail with the code fix of this PR, even though the fix allows the inspection results returned by the dialect to be correct for Actian databases (Ingres, Vector, Data Platform).

Many of the related dialect compliance suite tests fail when the database is VectorWise due to an unrelated issue, because the suite tests try to create a table with a self-referencing referential constraint, which is not allowed with X100 tables.

Testing - Dialect Compliance Suite

Ingres 12.0.0

Results	Passed	Failed	Errors	Skipped	Total
Before Fixes	548	94	33	859	1534
After Fixes	548	94	33	859	1534

Vector 6.3

Results	Passed	Failed	Errors	Skipped	Total
Before Fixes	323	68	785	358	1534
After Fixes	324	67	785	358	1534

It is worth mentioning that in my testing, the dialect compliance suite tests sometimes give differing results for multiple runs even if nothing is changed in between test runs. For example, if the test suite is run 10 times in a row without changing anything in between, the pass/fail rates for half of the runs might be different than the results for the other half of the runs. I have not spent much time trying to understand the reason for this behavior, although suspect it could be a timing issue with the creation/deletion of objects.

Testing - Simple Python program that reflects columns attributes

inspect_columns.py.txt

Given the following table definition in the attached program, results are show below.

sqlalchemy.Table(
    'house',
    metadata_obj,
    sqlalchemy.Column('house_id', sqlalchemy.Integer, primary_key=True),
    sqlalchemy.Column('address_id', sqlalchemy.Integer),
    sqlalchemy.Column('lot_id', sqlalchemy.Integer, comment='County record'),
    sqlalchemy.Column('data', sqlalchemy.String(10), unique=True),
    sqlalchemy.UniqueConstraint('house_id', 'address_id'), )

With the fixes of this PR, the attributes/values for nullable, autoincrement, and comment in the following inspection results are now correct.

Results with database: Ingres 12.0.0 GA

Inspection: [
{'name': 'house_id', 'nullable': False, 'default': 'next value for mhabiger"."$iiidentity_sequence_0000297"', 'type': Integer(), 'autoincrement': True, 'comment': None},
{'name': 'address_id', 'nullable': False, 'default': None, 'type': Integer(), 'autoincrement': False, 'comment': None},
{'name': 'lot_id', 'nullable': True, 'default': None, 'type': Integer(), 'autoincrement': False, 'comment': 'County record'},
{'name': 'data', 'nullable': False, 'default': None, 'type': VARCHAR(length=10), 'autoincrement': False, 'comment': None}]

Results with database: VectorWise 6.3 build 14614

Inspection: [
{'name': 'house_id', 'nullable': False, 'default': 'next value for "actian"."$iiidentity_sequence_0000364"', 'type': Integer(), 'autoincrement': True, 'comment': None},
{'name': 'address_id', 'nullable': True, 'default': None, 'type': Integer(), 'autoincrement': False, 'comment': None},
{'name': 'lot_id', 'nullable': True, 'default': None, 'type': Integer(), 'autoincrement': False, 'comment': 'County record'},
{'name': 'data', 'nullable': True, 'default': None, 'type': VARCHAR(length=10), 'autoincrement': False, 'comment': None}]

Results with database: Actian Data Platform 620.0.18 GCS

Inspection: [
{'name': 'house_id', 'nullable': False, 'default': 'next value for "vmxuser"."$iiidentity_sequence_0000384"', 'type': Integer(), 'autoincrement': True, 'comment': None},
{'name': 'address_id', 'nullable': True, 'default': None, 'type': Integer(), 'autoincrement': False, 'comment': None},
{'name': 'lot_id', 'nullable': True, 'default': None, 'type': Integer(), 'autoincrement': False, 'comment': 'County record'},
{'name': 'data', 'nullable': True, 'default': None, 'type': VARCHAR(length=10), 'autoincrement': False, 'comment': None}]

Client Environment

Microsoft Windows [Version 10.0.19045.4529]

Python 3.10.7

mock              5.1.0
packaging         24.1
pip               24.1.2
platformdirs      4.2.2
pluggy            1.5.0
psycopg2          2.9.9
pyodbc            5.1.0
pyproject-api     1.7.1
pypyodbc          1.3.6
pytest            8.3.1
setuptools        63.2.0
SQLAlchemy        2.0.30.dev0
sqlalchemy-ingres 0.0.8.dev1
tomli             2.0.1
tox               4.16.0
typing_extensions 4.12.2
virtualenv        20.26.3

Internal ticket II-14573

[clach04]

Not required, a comment here on what 6/7 represent could be helpful here.

[hab6]

Thanks for the review. Added comment for what row[6] and row[7] represent.