Add experimental support for db2. (#107)

* Draft integration of db2.

* Fix date gap.

* Add dependencies.

* Fix capitaliation tests.

* Add case distinction for varchar column.

* Add bash script for local development.

* Add changelog entry.

* Update CHANGELOG.rst

Co-authored-by: Ignacio Vergara Kausel <[email protected]>

* Add skip message.

---------

Co-authored-by: Ignacio Vergara Kausel <[email protected]>

.github/workflows/ci.yaml

@@ -155,6 +155,55 @@ jobs:
         with:
           file: ./coverage.xml
 
+
+  linux-integration_tests-db2:
+    name: "Linux - integration tests - Python ${{ matrix.PYTHON_VERSION }} - DB2"
+    runs-on: ubuntu-20.04
+    env:
+      CI: True
+    strategy:
+      fail-fast: false
+      matrix:
+        PYTHON_VERSION: [ '3.8', '3.9', '3.10' ]
+    services:
+      DB:
+        image: ibmcom/db2:11.5.5.1
+        env:
+          LICENSE: accept
+          DB2INSTANCE: db2inst1
+          DB2INST1_PASSWORD: password
+          DBNAME: testdb
+          UPDATEAVAIL: "NO"
+        options: --privileged
+        ports:
+          - 50000:50000
+
+    steps:
+      - name: Checkout branch
+        uses: actions/checkout@v3
+        with:
+          ref: ${{ github.head_ref }}
+      - name: Fetch full git history
+        run: git fetch --prune --unshallow
+      - uses: conda-incubator/setup-miniconda@v2
+        with:
+          python-version: ${{ matrix.PYTHON_VERSION }}
+          miniforge-variant: Mambaforge
+          miniforge-version: 4.11.0-2
+          use-mamba: true
+          environment-file: environment.yml
+          activate-environment: datajudge
+      - name: Run Integration Tests
+        shell: bash -l {0}
+        run: |
+          flit install -s
+          pytest --cov=datajudge --cov-report=xml --cov-append --backend=db2 tests/integration
+      - name: Generate code coverage report
+        uses: codecov/[email protected]
+        with:
+          file: ./coverage.xml
+
+
   linux-integration_tests-snowflake:
     name: "Linux - integration tests - Python ${{ matrix.PYTHON_VERSION }} - Snowflake"
     runs-on: ubuntu-latest
@@ -228,6 +277,7 @@ jobs:
         with:
           file: ./coverage.xml
 
+
   linux-integration_tests-impala-column-pt1:
     name: "Linux - integration tests - Python ${{ matrix.PYTHON_VERSION }} - Impala - pt1"
     runs-on: ubuntu-20.04

CHANGELOG.rst

@@ -7,7 +7,15 @@
 Changelog
 =========
 
-1.3.0 - 2022.xx.xx
+1.4.0 - 2022.02.24
+------------------
+
+**New features**
+
+- Add partial and experimental support for db2 as a backend.
+
+
+1.3.0 - 2022.01.17
 ------------------
 
 **New features**

environment.yml

@@ -25,3 +25,5 @@ dependencies:
   - flit
   - sphinx-autodoc-typehints
   - impyla
+  - ibm_db
+  - ibm_db_sa

src/datajudge/db_access.py

@@ -33,6 +33,10 @@ def is_impala(engine: sa.engine.Engine) -> bool:
     return engine.name == "impala"
 
 
+def is_db2(engine: sa.engine.Engine) -> bool:
+    return engine.name == "ibm_db_sa"
+
+
 def get_table_columns(table, column_names):
     return [table.c[column_name] for column_name in column_names]
 
@@ -421,6 +425,15 @@ def get_date_span(engine, ref, date_column_name):
                 )
             ]
         )
+    elif is_db2(engine):
+        selection = sa.select(
+            [
+                sa.func.days_between(
+                    sa.func.max(column),
+                    sa.func.min(column),
+                )
+            ]
+        )
     else:
         raise NotImplementedError(
             "Date spans not yet implemented for this sql dialect."
@@ -663,6 +676,14 @@ def get_date_gaps(
             )
             > legitimate_gap_size
         )
+    elif is_db2(engine):
+        gap_condition = (
+            sa.func.days_between(
+                start_table.c[start_column],
+                end_table.c[end_column],
+            )
+            > legitimate_gap_size
+        )
     else:
         raise NotImplementedError(f"Date gaps not yet implemented for {engine.name}.")
 

start_db2.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+set -e
+
+docker run -itd --name mydb2 --privileged=true -p 50000:50000 -e LICENSE=accept -e DB2INST1_PASSWORD=password -e DBNAME=testdb -v ~/database ibmcom/db2

tests/integration/conftest.py

@@ -8,7 +8,7 @@
 import sqlalchemy as sa
 from impala.dbapi import connect
 
-from datajudge.db_access import apply_patches, is_bigquery, is_impala, is_mssql
+from datajudge.db_access import apply_patches, is_bigquery, is_db2, is_impala, is_mssql
 
 TEST_DB_NAME = "tempdb"
 SCHEMA = "dbo"  # 'dbo' is the standard schema in mssql
@@ -30,6 +30,8 @@ def conn_creator():
 
     if backend == "postgres":
         connection_string = f"postgresql://datajudge:datajudge@{address}:5432/datajudge"
+    if backend == "db2":
+        connection_string = f"db2+ibm_db://db2inst1:password@{address}:50000/testdb"
     elif "mssql" in backend:
         connection_string = (
             f"mssql+pyodbc://sa:datajudge-123@{address}:1433/{TEST_DB_NAME}"
@@ -56,6 +58,12 @@ def conn_creator():
     return engine
 
 
+def _string_column(engine):
+    if is_db2(engine):
+        return sa.String(40)
+    return sa.String()
+
+
 @pytest.fixture(scope="module")
 def engine(backend):
     engine = get_engine(backend)
@@ -111,7 +119,7 @@ def mix_table1(engine, metadata):
     table_name = "mix_table1"
     columns = [
         sa.Column("col_int", sa.Integer()),
-        sa.Column("col_varchar", sa.String()),
+        sa.Column("col_varchar", _string_column(engine)),
         sa.Column("col_date", sa.DateTime()),
     ]
     data = [
@@ -131,7 +139,7 @@ def mix_table2(engine, metadata):
     table_name = "mix_table2"
     columns = [
         sa.Column("col_int", sa.Integer()),
-        sa.Column("col_varchar", sa.String()),
+        sa.Column("col_varchar", _string_column(engine)),
         sa.Column("col_date", sa.DateTime()),
     ]
     data = [
@@ -152,7 +160,7 @@ def mix_table2_pk(engine, metadata):
     table_name = "mix_table2_pk"
     columns = [
         sa.Column("col_int", sa.Integer(), primary_key=True),
-        sa.Column("col_varchar", sa.String()),
+        sa.Column("col_varchar", _string_column(engine)),
         sa.Column("col_date", sa.DateTime()),
     ]
     data = [
@@ -477,7 +485,7 @@ def unique_table1(engine, metadata):
     table_name = "unique_table1"
     columns = [
         sa.Column("col_int", sa.Integer()),
-        sa.Column("col_varchar", sa.String()),
+        sa.Column("col_varchar", _string_column(engine)),
     ]
     data = [{"col_int": i // 2, "col_varchar": f"hi{i // 3}"} for i in range(60)]
     data += [
@@ -493,7 +501,7 @@ def unique_table2(engine, metadata):
     table_name = "unique_table2"
     columns = [
         sa.Column("col_int", sa.Integer()),
-        sa.Column("col_varchar", sa.String()),
+        sa.Column("col_varchar", _string_column(engine)),
     ]
     data = [{"col_int": i // 2, "col_varchar": f"hi{i // 3}"} for i in range(40)]
     _handle_table(engine, metadata, table_name, columns, data)
@@ -503,7 +511,7 @@ def unique_table2(engine, metadata):
 @pytest.fixture(scope="module")
 def nested_table(engine, metadata):
     table_name = "nested_table"
-    columns = [sa.Column("nested_varchar", sa.String())]
+    columns = [sa.Column("nested_varchar", _string_column(engine))]
     data = [
         {"nested_varchar": "ABC#1,"},
         {"nested_varchar": "ABC#1,DEF#2,"},
@@ -517,7 +525,7 @@ def nested_table(engine, metadata):
 def varchar_table1(engine, metadata):
     table_name = "varchar_table1"
     columns = [
-        sa.Column("col_varchar", sa.String()),
+        sa.Column("col_varchar", _string_column(engine)),
     ]
     data = [{"col_varchar": "qq" * i} for i in range(1, 10)]
     data.append({"col_varchar": None})
@@ -529,7 +537,7 @@ def varchar_table1(engine, metadata):
 def varchar_table2(engine, metadata):
     table_name = "varchar_table2"
     columns = [
-        sa.Column("col_varchar", sa.String()),
+        sa.Column("col_varchar", _string_column(engine)),
     ]
     data = [{"col_varchar": "qq" * i} for i in range(2, 11)]
     _handle_table(engine, metadata, table_name, columns, data)
@@ -540,7 +548,7 @@ def varchar_table2(engine, metadata):
 def varchar_table_real(engine, metadata):
     table_name = "varchar_table_real"
     columns = [
-        sa.Column("col_varchar", sa.String()),
+        sa.Column("col_varchar", _string_column(engine)),
     ]
     data = [
         {"col_varchar": val}
@@ -754,6 +762,10 @@ def capitalization_table(engine, metadata):
         str_datatype = "STRING"
         # Impala supports primary keys but uses a different grammar.
         primary_key = ""
+    elif is_db2(engine):
+        str_datatype = "VARCHAR(20)"
+        # Primary key needs to be non-nullable.
+        primary_key = ""
     else:
         str_datatype = "TEXT"
     with engine.connect() as connection:
@@ -796,7 +808,15 @@ def pytest_addoption(parser):
     parser.addoption(
         "--backend",
         choices=(
-            ("mssql", "mssql-freetds", "postgres", "snowflake", "bigquery", "impala")
+            (
+                "mssql",
+                "mssql-freetds",
+                "postgres",
+                "snowflake",
+                "bigquery",
+                "impala",
+                "db2",
+            )
         ),
         help="which database backend to use to run the integration tests",
     )

tests/integration/test_column_capitalization.py

@@ -1,7 +1,7 @@
 import pytest
 
 from datajudge import Condition, WithinRequirement
-from datajudge.db_access import is_bigquery, is_impala, is_mssql, is_postgresql
+from datajudge.db_access import is_bigquery, is_db2, is_impala, is_mssql, is_postgresql
 
 # These tests
 
@@ -21,6 +21,10 @@ def test_column_existence(
         )
     if is_postgresql(engine):
         pytest.skip("Postgres interface always expects lower-cased columns.")
+    if is_db2(engine) and use_uppercase_query:
+        pytest.skip(
+            "Db2 interface transforms writes to lower-case, expects lower-case reads."
+        )
     (
         db_name,
         schema_name,