add test for a previously problematic scenario

test/sql/storage/compression/dictionary/dictionary_covers_validity.test

@@ -0,0 +1,72 @@
+# name: test/sql/storage/compression/dictionary/dictionary_covers_validity.test
+# group: [dictionary]
+
+load __TEST_DIR__/dictionary_covers_validity
+
+statement ok
+set checkpoint_threshold='10mb';
+
+statement ok
+CREATE TABLE tbl AS SELECT
+	{
+		'a': i,
+		'b': NULL::VARCHAR
+	} col
+FROM range(5000) t(i);
+
+statement ok
+INSERT INTO tbl VALUES (
+	{
+		'a': 10000,
+		'b': 'hello'
+	}
+);
+
+statement ok
+set force_compression='dictionary';
+
+statement ok
+force checkpoint;
+
+# Dictionary covers the validity, so the validity gets replaced with "Empty Validity"
+query II
+select segment_type, compression from pragma_storage_info('tbl');
+----
+VALIDITY	Constant
+BIGINT	BitPacking
+VALIDITY	Constant
+VARCHAR	Dictionary
+VALIDITY	Empty Validity
+
+statement ok
+INSERT INTO tbl VALUES (
+	{
+		'a': 10000,
+		'b': 'hello'
+	}
+);
+
+# Now force a different compression method, that doesn't cover the validity
+statement ok
+set force_compression='fsst';
+
+statement ok
+force checkpoint;
+
+# During checkpoint this will scan the dictionary compressed segments to get the validity
+# this then gets compressed as normal (since FSST does not cover the validity)
+query II
+select segment_type, compression from pragma_storage_info('tbl');
+----
+VALIDITY	Constant
+BIGINT	BitPacking
+VALIDITY	Constant
+VARCHAR	FSST
+VALIDITY	Roaring
+
+query I
+SELECT col FROM tbl ORDER BY col.a DESC LIMIT 3;
+----
+{'a': 10000, 'b': hello}
+{'a': 10000, 'b': hello}
+{'a': 4999, 'b': NULL}