Reflect expression-based indexes on PostgreSQL

The PostgreSQL dialect now supports reflection of expression based indexes.
The reflection is supported both when using
:meth:`_engine.Inspector.get_indexes` and when reflecting a
:class:`_schema.Table` using :paramref:`_schema.Table.autoload_with`.
Thanks to immerrr and Aidan Kane for the help on this ticket.

Fixes: #7442
Change-Id: I3e36d557235286c0f7f6d8276272ff9225058d48

1 files changed, 31 insertions, 0 deletions

diff --git a/lib/sqlalchemy/testing/assertions.py b/lib/sqlalchemy/testing/assertions.py
index 937706363..44e7e892f 100644
--- a/lib/sqlalchemy/testing/assertions.py
+++ b/lib/sqlalchemy/testing/assertions.py
@@ -838,3 +838,34 @@ class AssertsExecutionResults:
 
     def assert_statement_count(self, db, count):
         return self.assert_execution(db, assertsql.CountStatements(count))
+
+
+class ComparesIndexes:
+    def compare_table_index_with_expected(
+        self, table: schema.Table, expected: list, dialect_name: str
+    ):
+        eq_(len(table.indexes), len(expected))
+        idx_dict = {idx.name: idx for idx in table.indexes}
+        for exp in expected:
+            idx = idx_dict[exp["name"]]
+            eq_(idx.unique, exp["unique"])
+            cols = [c for c in exp["column_names"] if c is not None]
+            eq_(len(idx.columns), len(cols))
+            for c in cols:
+                is_true(c in idx.columns)
+            exprs = exp.get("expressions")
+            if exprs:
+                eq_(len(idx.expressions), len(exprs))
+                for idx_exp, expr, col in zip(
+                    idx.expressions, exprs, exp["column_names"]
+                ):
+                    if col is None:
+                        eq_(idx_exp.text, expr)
+            if (
+                exp.get("dialect_options")
+                and f"{dialect_name}_include" in exp["dialect_options"]
+            ):
+                eq_(
+                    idx.dialect_options[dialect_name]["include"],
+                    exp["dialect_options"][f"{dialect_name}_include"],
+                )