Fix PostgreSQL search index expressions

Make sure to merge the indexes on the client side because the server
will not accept parameters in the CREATE INDEX statement.

django/contrib/postgres/search.py

@@ -5,6 +5,20 @@
 from django.db.models.functions import Cast, Coalesce
 
 
+def merge_client_side(connection, query, params):
+    """
+    Merge an sql expression and a sequence of parameters on the client side
+    """
+    if connection.psycopg_version[0] > 2:
+        from psycopg import sql
+    else:
+        from psycopg2 import sql
+
+    query = sql.SQL(query.replace("{", "{{").replace("}", "}}").replace("%s", "{}"))
+    merged = query.format(*map(sql.Literal, params))
+    return merged.as_string(connection.cursor().cursor)
+
+
 class SearchVectorExact(Lookup):
     lookup_name = 'exact'
 
@@ -116,7 +130,11 @@ def as_sql(self, compiler, connection, function=None, template=None):
         if clone.weight:
             weight_sql, extra_params = compiler.compile(clone.weight)
             sql = 'setweight({}, {})'.format(sql, weight_sql)
-        return sql, config_params + params + extra_params
+
+        # These parameters must be bound on the client side because we may
+        # want to create an index on this expression.
+        sql = merge_client_side(connection, sql, config_params + params + extra_params)
+        return sql, []
 
 
 class CombinedSearchVector(SearchVectorCombinable, CombinedExpression):
@@ -266,10 +284,8 @@ def as_sql(self, compiler, connection, function=None, template=None):
         if self.options:
             # getquoted() returns a quoted bytestring of the adapted value.
             options_params.append(', '.join(
-                '%s=%s' % (
-                    option,
-                    psycopg2.extensions.adapt(value).getquoted().decode(),
-                ) for option, value in self.options.items()
+                merge_client_side(connection, "%s=%%s" % option, [value])
+                for option, value in self.options.items()
             ))
             options_sql = ', %s'
         sql, params = super().as_sql(