Add test cases for indexam operations not currently covered.

That includes VACUUM on GIN, GiST and SP-GiST indexes, and B-tree indexes
large enough to cause page deletions in B-tree. Plus some other special
cases.

After this patch, the regression tests generate all different WAL record
types. Not all branches within the redo functions are covered, but it's a
step forward.

src/test/regress/sql/spgist.sql

@@ -0,0 +1,50 @@
+--
+-- Test SP-GiST indexes.
+--
+-- There are other tests to test different SP-GiST opclasses. This is for
+-- testing SP-GiST code itself.
+
+create table spgist_point_tbl(id int4, p point);
+create index spgist_point_idx on spgist_point_tbl using spgist(p);
+
+-- Test vacuum-root operation. It gets invoked when the root is also a leaf,
+-- i.e. the index is very small.
+insert into spgist_point_tbl (id, p)
+select g, point(g*10, g*10) from generate_series(1, 10) g;
+delete from spgist_point_tbl where id < 5;
+vacuum spgist_point_tbl;
+
+-- Insert more data, to make the index a few levels deep.
+insert into spgist_point_tbl (id, p)
+select g,      point(g*10, g*10) from generate_series(1, 10000) g;
+insert into spgist_point_tbl (id, p)
+select g+100000, point(g*10+1, g*10+1) from generate_series(1, 10000) g;
+
+-- To test vacuum, delete some entries from all over the index.
+delete from spgist_point_tbl where id % 2 = 1;
+
+-- And also delete some concentration of values. (SP-GiST doesn't currently
+-- attempt to delete pages even when they become empty, but if it did, this
+-- would exercise it)
+delete from spgist_point_tbl where id < 10000;
+
+vacuum spgist_point_tbl;
+
+
+-- The point opclass's choose method only uses the spgMatchNode action,
+-- so the other actions are not tested by the above. Create an index using
+-- text opclass, which uses the others actions.
+
+create table spgist_text_tbl(id int4, t text);
+create index spgist_text_idx on spgist_text_tbl using spgist(t);
+
+insert into spgist_text_tbl (id, t)
+select g, 'f' || repeat('o', 100) || g from generate_series(1, 10000) g
+union all
+select g, 'baaaaaaaaaaaaaar' || g from generate_series(1, 1000) g;
+
+-- Do a lot of insertions that have to split an existing node. Hopefully
+-- one of these will cause the page to run out of space, causing the inner
+-- tuple to be moved to another page.
+insert into spgist_text_tbl (id, t)
+select -g, 'f' || repeat('o', 100-g) || 'surprise' from generate_series(1, 100) g;