tablesample test failure with small TOAST_TUPLE_THRESHOLD

Today, I tried compiling with:

-#define TOAST_TUPLE_THRESHOLD MaximumBytesPerTuple(TOAST_TUPLES_PER_PAGE)
+#define TOAST_TUPLE_THRESHOLD 100

Most of the regression tests pass just fine, but the tablesample one
experiences numerous failures. For example:

SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (0);
id
----
! 3
! 4
! 5
! 6
! 7
! 8
! (6 rows)

SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (0);
id
--- 5,11 ----
SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (0);
id
----
! (0 rows)

SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (0);
id

Most of the failures are due to table-sampling that previously
returned rows no longer returning any rows. I don't know why that
should happen, or whether it's expected.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company