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README.md

@@ -372,31 +372,35 @@ pg8000.exceptions.DatabaseError: ...
 
 ```
 
-instead you can write it using the [unnest
-](https://www.postgresql.org/docs/current/functions-array.html) function:
+the most straightforward way to get around this problem is to rewrie the query using the [`ANY`](
+https://www.postgresql.org/docs/current/functions-comparisons.html#FUNCTIONS-COMPARISONS-ANY-SOME)
+function:
 
 ```python
 >>> import pg8000.native
 >>>
 >>> con = pg8000.native.Connection("postgres", password="cpsnow")
 >>>
->>> con.run(
-...     "SELECT 'silo 1' WHERE 'a' IN (SELECT unnest(CAST(:v as varchar[])))",
-...     v=['a', 'b'])
+>>> con.run("SELECT 'silo 1' WHERE 'a' = ANY(:v)", v=['a', 'b'])
 [['silo 1']]
 >>> con.close()
 
 ```
 
-or `any`:
+However, using the array variant of `ANY` [may cause a performance problem](
+https://stackoverflow.com/questions/34627026/in-vs-any-operator-in-postgresql) and so
+you can use the [subquery variant of `IN`](
+https://www.postgresql.org/docs/current/functions-subquery.html#FUNCTIONS-SUBQUERY-IN)
+with the [unnest
+](https://www.postgresql.org/docs/current/functions-array.html) function:
 
 ```python
 >>> import pg8000.native
 >>>
 >>> con = pg8000.native.Connection("postgres", password="cpsnow")
 >>>
 >>> con.run(
-...     "SELECT 'silo 1' WHERE 'a' = any(:v)",
+...     "SELECT 'silo 1' WHERE 'a' IN (SELECT unnest(CAST(:v as varchar[])))",
 ...     v=['a', 'b'])
 [['silo 1']]
 >>> con.close()