Add DatabaseDialect and implement identifiers truncation (#54)

* Added a DatabaseDialect class hierarchy (base, postgresql, mssql, mysql, duckdb), one subclass per backend, to abstract db specific logic and avoid conditionnals scattered in the code
* Implement truncation of database identifiers, because long names was an issue frequently found especially with postgresql. Each db dialect sets its own limit
* Remove Python 3.9 support (EOL) and add Python 3.14 to the test matrix
* Bump version
---------

Co-authored-by: cre-os <opensource@cre.fr>

Author: martinv13

.github/workflows/python-package.yml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
 
     steps:
     - uses: actions/checkout@v4

docs/configuring.md

@@ -79,16 +79,16 @@ table, or a child table.
 ### Data types
 
 By default, the data type defined in the database table for each column is based on a mapping between the data type 
-indicated in the XSD and a corresponding `sqlalchemy` type implemented in the following three functions:
+indicated in the XSD and a corresponding `sqlalchemy` type implemented in the following three methods:
 
-??? info "Default: `types_mapping_default`"
-    ::: xml2db.table.column.types_mapping_default
+??? info "Default: `DatabaseDialect.column_type`"
+    ::: xml2db.dialect.base.DatabaseDialect.column_type
 
-??? info "MySQL: `types_mapping_mysql`"
-    ::: xml2db.table.column.types_mapping_mysql
+??? info "MySQL: `MySQLDialect.column_type`"
+    ::: xml2db.dialect.mysql.MySQLDialect.column_type
 
-??? info "MSSQL: `types_mapping_mssql`"
-    ::: xml2db.table.column.types_mapping_mssql
+??? info "MSSQL: `MSSQLDialect.column_type`"
+    ::: xml2db.dialect.mssql.MSSQLDialect.column_type
 
 You may override this mapping by specifying a column type for any field in the model config. Custom column types are 
 defined as `sqlalchemy` types and will be passed to the `sqlalchemy.Column` constructor as is.

pyproject.toml

@@ -4,13 +4,13 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "xml2db"
-version = "0.12.6"
+version = "0.13.0"
 authors = [
   { name="Commission de régulation de l'énergie", email="opensource@cre.fr" },
 ]
 description = "Import complex XML files to a relational database"
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 classifiers = [
     "Programming Language :: Python :: 3",
     "License :: OSI Approved :: MIT License",

src/xml2db/dialect/__init__.py

@@ -0,0 +1,65 @@
+"""Backend-specific dialect classes for xml2db.
+
+This package centralises all database-backend-specific behaviour that was
+previously scattered across the codebase as ``if db_type == "..."``
+conditionals. Each supported backend has a dedicated subclass of
+:class:`~xml2db.dialect.base.DatabaseDialect`. Unknown backends fall back to
+the base class, which provides safe, generic defaults.
+
+Usage::
+
+    from xml2db.dialect import get_dialect
+
+    dialect = get_dialect("postgresql")
+    physical_name = dialect.db_identifier("some_very_long_xsd_derived_name")
+
+The registry is a plain dict so that third-party code (or tests) can register
+custom dialects without subclassing anything in xml2db::
+
+    from xml2db.dialect import DIALECT_REGISTRY
+    from mypackage import OracleDialect
+
+    DIALECT_REGISTRY["oracle"] = OracleDialect
+"""
+
+from .base import DatabaseDialect
+from .duckdb import DuckDBDialect
+from .mssql import MSSQLDialect
+from .mysql import MySQLDialect
+from .postgresql import PostgreSQLDialect
+
+__all__ = [
+    "DatabaseDialect",
+    "DuckDBDialect",
+    "MSSQLDialect",
+    "MySQLDialect",
+    "PostgreSQLDialect",
+    "DIALECT_REGISTRY",
+    "get_dialect",
+]
+
+# Maps the SQLAlchemy dialect name (as returned by engine.dialect.name) to
+# the corresponding DatabaseDialect subclass.
+DIALECT_REGISTRY: dict[str, type[DatabaseDialect]] = {
+    "postgresql": PostgreSQLDialect,
+    "mssql": MSSQLDialect,
+    "mysql": MySQLDialect,
+    "mariadb": MySQLDialect,  # SQLAlchemy reports MariaDB as "mariadb"
+    "duckdb": DuckDBDialect,
+}
+
+
+def get_dialect(db_type: str | None) -> DatabaseDialect:
+    """Return a :class:`DatabaseDialect` instance for the given backend name.
+
+    Args:
+        db_type: The SQLAlchemy dialect name, e.g. ``"postgresql"``,
+            ``"mssql"``, ``"mysql"``, ``"duckdb"``. ``None`` or any
+            unrecognised string falls back to the base
+            :class:`DatabaseDialect`, which uses safe generic defaults.
+
+    Returns:
+        An instantiated :class:`DatabaseDialect` (or subclass) ready for use.
+    """
+    cls = DIALECT_REGISTRY.get(db_type, DatabaseDialect)
+    return cls()