Add quote_relation_name support utility function

Author: amotl

CHANGES.md

@@ -1,7 +1,7 @@
 # Changelog
 
-
 ## Unreleased
+- Added `quote_relation_name` support utility function
 
 ## 2024/06/25 0.38.0
 - Added/reactivated documentation as `sqlalchemy-cratedb`

src/sqlalchemy_cratedb/support/__init__.py

@@ -4,12 +4,13 @@
     patch_autoincrement_timestamp,
     refresh_after_dml,
 )
-from sqlalchemy_cratedb.support.util import refresh_dirty, refresh_table
+from sqlalchemy_cratedb.support.util import quote_relation_name, refresh_dirty, refresh_table
 
 __all__ = [
     check_uniqueness_factory,
     insert_bulk,
     patch_autoincrement_timestamp,
+    quote_relation_name,
     refresh_after_dml,
     refresh_dirty,
     refresh_table,

src/sqlalchemy_cratedb/support/util.py

@@ -3,13 +3,19 @@
 
 import sqlalchemy as sa
 
+from sqlalchemy_cratedb.dialect import CrateDialect
+
 if t.TYPE_CHECKING:
     try:
         from sqlalchemy.orm import DeclarativeBase
     except ImportError:
         pass
 
 
+# An instance of the dialect used for quoting purposes.
+identifier_preparer = CrateDialect().identifier_preparer
+
+
 def refresh_table(
     connection, target: t.Union[str, "DeclarativeBase", "sa.sql.selectable.TableClause"]
 ):
@@ -41,3 +47,36 @@ def refresh_dirty(session, flush_context=None):
     dirty_classes = {entity.__class__ for entity in dirty_entities}
     for class_ in dirty_classes:
         refresh_table(session, class_)
+
+
+def quote_relation_name(ident: str) -> str:
+    """
+    Quote a simple or full-qualified table/relation name, when needed.
+
+    Simple:         <table>
+    Full-qualified: <schema>.<table>
+
+    Happy path examples:
+
+        foo => foo
+        Foo => "Foo"
+        "Foo" => "Foo"
+        foo.bar => foo.bar
+        foo-bar.baz_qux => "foo-bar".baz_qux
+
+    Such input strings will not be modified:
+
+        "foo.bar" => "foo.bar"
+    """
+
+    # If a quote exists at the beginning or the end of the input string,
+    # let's consider that the relation name has been quoted already.
+    if ident.startswith('"') or ident.endswith('"'):
+        return ident
+
+    # If a dot is included, it's a full-qualified identifier like <schema>.<table>.
+    # It needs to be split, in order to apply identifier quoting properly.
+    parts = ident.split(".")
+    if len(parts) > 3:
+        raise ValueError(f"Invalid relation name, too many parts: {ident}")
+    return ".".join(map(identifier_preparer.quote, parts))

tests/test_support_util.py

@@ -0,0 +1,51 @@
+import pytest
+
+from sqlalchemy_cratedb.support import quote_relation_name
+
+
+def test_quote_relation_name_once():
+    """
+    Verify quoting a simple or full-qualified relation name.
+    """
+
+    # Table name only.
+    assert quote_relation_name("my_table") == "my_table"
+    assert quote_relation_name("my-table") == '"my-table"'
+    assert quote_relation_name("MyTable") == '"MyTable"'
+    assert quote_relation_name('"MyTable"') == '"MyTable"'
+
+    # Schema and table name.
+    assert quote_relation_name("my_schema.my_table") == "my_schema.my_table"
+    assert quote_relation_name("my-schema.my_table") == '"my-schema".my_table'
+    assert quote_relation_name('"wrong-quoted-fqn.my_table"') == '"wrong-quoted-fqn.my_table"'
+    assert quote_relation_name('"my_schema"."my_table"') == '"my_schema"."my_table"'
+
+    # Catalog, schema, and table name.
+    assert quote_relation_name("crate.doc.t01") == "crate.doc.t01"
+
+
+def test_quote_relation_name_twice():
+    """
+    Verify quoting a relation name twice does not cause any harm.
+    """
+    input_fqn = "foo-bar.baz_qux"
+    output_fqn = '"foo-bar".baz_qux'
+    assert quote_relation_name(input_fqn) == output_fqn
+    assert quote_relation_name(output_fqn) == output_fqn
+
+
+def test_quote_relation_name_reserved_keywords():
+    """
+    Verify quoting a simple relation name that is a reserved keyword.
+    """
+    assert quote_relation_name("table") == '"table"'
+    assert quote_relation_name("true") == '"true"'
+    assert quote_relation_name("select") == '"select"'
+
+
+def test_quote_relation_name_with_invalid_fqn():
+    """
+    Verify quoting a relation name with an invalid fqn raises an error.
+    """
+    with pytest.raises(ValueError):
+        quote_relation_name("too-many.my-db.my-schema.my-table")