superset2/tests/unit_tests/db_engine_specs/test_redshift.py

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from datetime import datetime
from typing import Optional

import pytest
import sqlalchemy as sa
from sqlalchemy.dialects import postgresql

from superset.db_engine_specs.redshift import RedshiftEngineSpec
from tests.unit_tests.db_engine_specs.utils import assert_convert_dttm
from tests.unit_tests.fixtures.common import dttm  # noqa: F401


@pytest.mark.parametrize(
    "target_type,expected_result",
    [
        ("Date", "TO_DATE('2019-01-02', 'YYYY-MM-DD')"),
        (
            "DateTime",
            "TO_TIMESTAMP('2019-01-02 03:04:05.678900', 'YYYY-MM-DD HH24:MI:SS.US')",
        ),
        (
            "TimeStamp",
            "TO_TIMESTAMP('2019-01-02 03:04:05.678900', 'YYYY-MM-DD HH24:MI:SS.US')",
        ),
        ("UnknownType", None),
    ],
)
def test_convert_dttm(
    target_type: str,
    expected_result: Optional[str],
    dttm: datetime,  # noqa: F811
) -> None:
    from superset.db_engine_specs.redshift import (
        RedshiftEngineSpec as spec,  # noqa: N813
    )

    assert_convert_dttm(spec, target_type, expected_result, dttm)


@pytest.mark.parametrize(
    "table_name,schema_name,expected_table,expected_schema",
    [
        ("BPO_mytest_2", "MySchema", "bpo_mytest_2", "myschema"),
        ("MY_TABLE", None, "my_table", None),
        ("already_lower", "lower_schema", "already_lower", "lower_schema"),
    ],
)
def test_normalize_table_name_for_upload(
    table_name: str,
    schema_name: Optional[str],
    expected_table: str,
    expected_schema: Optional[str],
) -> None:
    """
    Test that table and schema names are normalized to lowercase for Redshift.

    Redshift folds unquoted identifiers to lowercase, so we need to normalize
    table names to ensure consistent behavior when checking table existence
    and performing replace operations.
    """
    normalized_table, normalized_schema = (
        RedshiftEngineSpec.normalize_table_name_for_upload(table_name, schema_name)
    )

    assert normalized_table == expected_table
    assert normalized_schema == expected_schema


def test_extended_aggregation_func_inherited_from_postgres() -> None:
    """
    Redshift is a Postgres fork and inherits STDDEV_SAMP/VAR_SAMP from
    `PostgresBaseEngineSpec` -- its documented SQL function reference matches
    Postgres for these functions, though this has not been separately
    verified against a live Redshift instance (see the SIP doc for caveats).

    MEDIAN is overridden rather than inherited (see
    `RedshiftEngineSpec._extended_aggregations`): unlike Postgres, Redshift
    documents a native `MEDIAN(x)` function, so Redshift emits that directly
    instead of Postgres's `percentile_cont(0.5) WITHIN GROUP (ORDER BY col)`
    spelling -- which also sidesteps Redshift's documented restriction
    against more than one sort-based aggregate with a different ORDER BY in
    the same query, e.g. `MEDIAN(sales)` alongside `MEDIAN(margin)`.
    """
    from sqlalchemy import column

    col = column("sales")

    median_func = RedshiftEngineSpec.get_extended_aggregation_func("MEDIAN")
    assert median_func is not None
    assert (
        str(median_func(col).compile(compile_kwargs={"literal_binds": True}))
        == "median(sales)"
    )

    for aggregate in ("STDDEV_SAMP", "VAR_SAMP"):
        assert RedshiftEngineSpec.get_extended_aggregation_func(aggregate) is not None


def test_normalize_custom_sql_metric_date_trunc_unit() -> None:
    expression: str = "DATE_TRUNC('QUARTER', created_at)"

    assert RedshiftEngineSpec.normalize_custom_sql_metric(expression) == (
        "DATE_TRUNC('quarter', created_at)"
    )


def test_date_trunc_metric_matches_quarter_grouping_in_complete_query() -> None:
    metric: sa.ColumnElement = sa.literal_column(
        RedshiftEngineSpec.normalize_custom_sql_metric(
            "CASE WHEN DATE_TRUNC('QUARTER', created_at) = '2024-01-01' "
            "THEN COUNT(*) END"
        )
    ).label("quarter_metric")
    quarter: sa.ColumnElement = RedshiftEngineSpec.get_timestamp_expr(
        col=sa.column("created_at"),
        pdf=None,
        time_grain="P3M",
    )
    query: sa.Select = (
        sa.select(quarter, metric).select_from(sa.table("orders")).group_by(quarter)
    )

    sql: str = str(query.compile(dialect=postgresql.dialect()))

    assert "DATE_TRUNC('QUARTER'" not in sql
    assert sql.count("DATE_TRUNC('quarter'") >= 2