Add transformer for AWS DMS to CrateDB SQL

- PostgreSQL full-load and CDC

CHANGES.md

@@ -1,6 +1,7 @@
 # Changelog
 
 ## Unreleased
+- Added transformer for AWS DMS to CrateDB SQL
 
 ## 2024/07/19 v0.0.2
 - Added transformer for MongoDB CDC to CrateDB SQL conversion

pyproject.toml

@@ -101,6 +101,7 @@ dynamic = [
   "version",
 ]
 dependencies = [
+  "attrs<24",
   "simplejson<4",
   "toolz<0.13",
 ]

src/commons_codec/exception.py

@@ -0,0 +1,6 @@
+class MessageFormatError(Exception):
+    pass
+
+
+class UnknownOperationError(Exception):
+    pass

src/commons_codec/model.py

@@ -0,0 +1,47 @@
+from enum import StrEnum, auto
+
+from attrs import define
+
+
+@define(frozen=True)
+class TableAddress:
+    schema: str
+    table: str
+
+    @property
+    def fqn(self):
+        if not self.schema:
+            raise ValueError("Unable to compute a full-qualified table name without schema name")
+        return f"{self.quote_identifier(self.schema)}.{self.quote_identifier(self.table)}"
+
+    @staticmethod
+    def quote_identifier(name: str) -> str:
+        """
+        Poor man's table quoting.
+
+        TODO: Better use or vendorize canonical table quoting function from CrateDB Toolkit, when applicable.
+        """
+        if name and '"' not in name:
+            name = f'"{name}"'
+        return name
+
+
+class ColumnType(StrEnum):
+    MAP = auto()
+
+
+@define(frozen=True)
+class ColumnTypeMap:
+    column: str
+    type: ColumnType
+
+
+class PrimaryKeyStore(dict):
+    pass
+
+
+class ColumnTypeMapStore(dict):
+    def add(self, table: TableAddress, column: str, type_: ColumnType):
+        self.setdefault(table, {})
+        self[table][column] = type_
+        return self

src/commons_codec/transform/aws_dms.py

@@ -0,0 +1,155 @@
+# Copyright (c) 2023-2024, The Kotori Developers and contributors.
+# Distributed under the terms of the LGPLv3 license, see LICENSE.
+
+# ruff: noqa: S608 FIXME: Possible SQL injection vector through string-based query construction
+
+import logging
+import typing as t
+
+import simplejson as json
+
+from commons_codec.exception import MessageFormatError, UnknownOperationError
+from commons_codec.model import ColumnType, ColumnTypeMapStore, PrimaryKeyStore, TableAddress
+
+logger = logging.getLogger(__name__)
+
+
+class DMSTranslatorCrateDBRecord:
+    """
+    Translate DMS full-load and cdc events into CrateDB SQL statements.
+    """
+
+    # Define name of the column where CDC's record data will get materialized into.
+    DATA_COLUMN = "data"
+
+    def __init__(
+        self,
+        record: t.Dict[str, t.Any],
+        container: "DMSTranslatorCrateDB",
+    ):
+        self.record = record
+        self.container = container
+
+        self.metadata: t.Dict[str, t.Any] = self.record.get("metadata", {})
+        self.control: t.Dict[str, t.Any] = self.record.get("control", {})
+        self.data: t.Dict[str, t.Any] = self.record.get("data", {})
+
+        self.operation: t.Union[str, None] = self.metadata.get("operation")
+
+        self.schema: t.Union[str, None] = self.metadata.get("schema-name")
+        self.table: t.Union[str, None] = self.metadata.get("table-name")
+
+        # Tweaks.
+
+        # Divert special tables like `awsdms_apply_exceptions` to a dedicated schema.
+        # Relevant CDC events are delivered with an empty table name, so some valid
+        # name needs to be selected anyway. The outcome of this is that AWS DMS special
+        # tables will be created within the sink database, like `dms.awsdms_apply_exceptions`.
+        if self.table and self.table.startswith("awsdms_"):
+            self.schema = "dms"
+
+        # Sanity checks.
+        if not self.metadata or not self.operation:
+            message = "Record not in DMS format: metadata and/or operation is missing"
+            logger.error(message)
+            raise MessageFormatError(message)
+
+        if not self.schema or not self.table:
+            message = f"Schema or table name missing or empty: schema={self.schema}, table={self.table}"
+            logger.error(message)
+            raise MessageFormatError(message)
+
+        self.address: TableAddress = TableAddress(schema=self.schema, table=self.table)
+
+        self.container.primary_keys.setdefault(self.address, [])
+        self.container.column_types.setdefault(self.address, {})
+        self.primary_keys: t.List[str] = self.container.primary_keys[self.address]
+        self.column_types: t.Dict[str, ColumnType] = self.container.column_types[self.address]
+
+    def to_sql(self) -> str:
+        if self.operation == "create-table":
+            pks = self.control.get("table-def", {}).get("primary-key")
+            if pks:
+                self.primary_keys += pks
+            # TODO: What about dropping tables first?
+            return f"CREATE TABLE IF NOT EXISTS {self.address.fqn} ({self.DATA_COLUMN} OBJECT(DYNAMIC));"
+
+        elif self.operation in ["load", "insert"]:
+            values_clause = self.record_to_values()
+            sql = f"INSERT INTO {self.address.fqn} ({self.DATA_COLUMN}) VALUES ('{values_clause}');"
+
+        elif self.operation == "update":
+            values_clause = self.record_to_values()
+            where_clause = self.keys_to_where()
+            sql = f"UPDATE {self.address.fqn} SET {self.DATA_COLUMN} = '{values_clause}' WHERE {where_clause};"
+
+        elif self.operation == "delete":
+            where_clause = self.keys_to_where()
+            sql = f"DELETE FROM {self.address.fqn} WHERE {where_clause};"
+
+        else:
+            message = f"Unknown CDC event operation: {self.operation}"
+            logger.warning(message)
+            raise UnknownOperationError(message)
+
+        return sql
+
+    def record_to_values(self) -> str:
+        """
+        Apply type translations to record, and serialize to JSON.
+
+        IN (top-level stripped):
+        "data": {"age": 30, "attributes": '{"foo": "bar"}', "id": 42, "name": "John"}
+
+        OUT:
+        {"age": 30, "attributes": {"foo": "bar"}, "id": 42, "name": "John"}
+        """
+        for column_name, column_type in self.column_types.items():
+            if column_name in self.data:
+                value = self.data[column_name]
+                # DMS marshals JSON|JSONB to CLOB, aka. string. Apply a countermeasure.
+                if column_type is ColumnType.MAP and isinstance(value, str):
+                    value = json.loads(value)
+                self.data[column_name] = value
+        return json.dumps(self.data)
+
+    def keys_to_where(self) -> str:
+        """
+        Produce an SQL WHERE clause based on primary key definition and current record's data.
+        """
+        if not self.primary_keys:
+            raise ValueError("Unable to invoke DML operation without primary key information")
+        constraints: t.List[str] = []
+        for key_name in self.primary_keys:
+            key_value = self.data.get(key_name)
+            # FIXME: Does the quoting of the value on the right hand side need to take the data type into account?
+            constraint = f"{self.DATA_COLUMN}['{key_name}'] = '{key_value}'"
+            constraints.append(constraint)
+        return " AND ".join(constraints)
+
+
+class DMSTranslatorCrateDB:
+    """
+    Translate AWS DMS event messages into CrateDB SQL statements that materialize them again.
+
+    The SQL DDL schema for CrateDB:
+    CREATE TABLE <tablename> (data OBJECT(DYNAMIC));
+
+    Blueprint:
+    https://www.cockroachlabs.com/docs/stable/aws-dms
+    """
+
+    def __init__(
+        self,
+        primary_keys: PrimaryKeyStore = None,
+        column_types: ColumnTypeMapStore = None,
+    ):
+        self.primary_keys = primary_keys or PrimaryKeyStore()
+        self.column_types = column_types or ColumnTypeMapStore()
+
+    def to_sql(self, record: t.Dict[str, t.Any]) -> str:
+        """
+        Produce INSERT|UPDATE|DELETE SQL statement from load|insert|update|delete CDC event record.
+        """
+        record_decoded = DMSTranslatorCrateDBRecord(record=record, container=self)
+        return record_decoded.to_sql()

tests/test_model.py

@@ -0,0 +1,14 @@
+import pytest
+from commons_codec.model import TableAddress
+
+
+def test_table_address_success():
+    ta = TableAddress(schema="foo", table="bar")
+    assert ta.fqn == '"foo"."bar"'
+
+
+def test_table_address_failure():
+    ta = TableAddress(schema=None, table="bar")
+    with pytest.raises(ValueError) as ex:
+        _ = ta.fqn
+        assert ex.match("adcdc")