1 files changed, 54 insertions, 0 deletions
diff --git a/sqlglot/optimizer/qualify_tables.py b/sqlglot/optimizer/qualify_tables.py
new file mode 100644
index 0000000..9f8b9f5
--- /dev/null
+++ b/sqlglot/optimizer/qualify_tables.py
@@ -0,0 +1,54 @@
+import itertools
+
+from sqlglot import alias, exp
+from sqlglot.optimizer.scope import traverse_scope
+
+
+def qualify_tables(expression, db=None, catalog=None):
+    """
+    Rewrite sqlglot AST to have fully qualified tables.
+
+    Example:
+        >>> import sqlglot
+        >>> expression = sqlglot.parse_one("SELECT 1 FROM tbl")
+        >>> qualify_tables(expression, db="db").sql()
+        'SELECT 1 FROM db.tbl AS tbl'
+
+    Args:
+        expression (sqlglot.Expression): expression to qualify
+        db (str): Database name
+        catalog (str): Catalog name
+    Returns:
+        sqlglot.Expression: qualified expression
+    """
+    sequence = itertools.count()
+
+    for scope in traverse_scope(expression):
+        for derived_table in scope.ctes + scope.derived_tables:
+            if not derived_table.args.get("alias"):
+                alias_ = f"_q_{next(sequence)}"
+                derived_table.set(
+                    "alias", exp.TableAlias(this=exp.to_identifier(alias_))
+                )
+                scope.rename_source(None, alias_)
+
+        for source in scope.sources.values():
+            if isinstance(source, exp.Table):
+                identifier = isinstance(source.this, exp.Identifier)
+
+                if identifier:
+                    if not source.args.get("db"):
+                        source.set("db", exp.to_identifier(db))
+                    if not source.args.get("catalog"):
+                        source.set("catalog", exp.to_identifier(catalog))
+
+                if not isinstance(source.parent, exp.Alias):
+                    source.replace(
+                        alias(
+                            source.copy(),
+                            source.this if identifier else f"_q_{next(sequence)}",
+                            table=True,
+                        )
+                    )
+
+    return expression