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diff --git a/sqlglot/optimizer/optimizer.py b/sqlglot/optimizer/optimizer.py
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+++ b/sqlglot/optimizer/optimizer.py
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+from sqlglot.optimizer.eliminate_subqueries import eliminate_subqueries
+from sqlglot.optimizer.expand_multi_table_selects import expand_multi_table_selects
+from sqlglot.optimizer.isolate_table_selects import isolate_table_selects
+from sqlglot.optimizer.normalize import normalize
+from sqlglot.optimizer.optimize_joins import optimize_joins
+from sqlglot.optimizer.pushdown_predicates import pushdown_predicates
+from sqlglot.optimizer.pushdown_projections import pushdown_projections
+from sqlglot.optimizer.qualify_columns import qualify_columns
+from sqlglot.optimizer.qualify_tables import qualify_tables
+from sqlglot.optimizer.quote_identities import quote_identities
+from sqlglot.optimizer.unnest_subqueries import unnest_subqueries
+
+
+def optimize(expression, schema=None, db=None, catalog=None):
+    """
+    Rewrite a sqlglot AST into an optimized form.
+
+    Args:
+        expression (sqlglot.Expression): expression to optimize
+        schema (dict|sqlglot.optimizer.Schema): database schema.
+            This can either be an instance of `sqlglot.optimizer.Schema` or a mapping in one of
+            the following forms:
+                1. {table: {col: type}}
+                2. {db: {table: {col: type}}}
+                3. {catalog: {db: {table: {col: type}}}}
+        db (str): specify the default database, as might be set by a `USE DATABASE db` statement
+        catalog (str): specify the default catalog, as might be set by a `USE CATALOG c` statement
+    Returns:
+        sqlglot.Expression: optimized expression
+    """
+    expression = expression.copy()
+    expression = qualify_tables(expression, db=db, catalog=catalog)
+    expression = isolate_table_selects(expression)
+    expression = qualify_columns(expression, schema)
+    expression = pushdown_projections(expression)
+    expression = normalize(expression)
+    expression = unnest_subqueries(expression)
+    expression = expand_multi_table_selects(expression)
+    expression = pushdown_predicates(expression)
+    expression = optimize_joins(expression)
+    expression = eliminate_subqueries(expression)
+    expression = quote_identities(expression)
+    return expression