Make zstd tests more deterministic

The current tests would diff on the SELECT queries containing ORDER BY
LIMIT on a gpdemo cluster (seen on my MacOS Mojave laptop and on a
CentOS 6 & 7 VM). Most likely the test answer file was created from a
cluster that was not the test standard 3 primary segment configuration
so the SELECT may output differently.

Co-authored-by: Karen Huddleston <khuddleston@pivotal.io>

gpcontrib/zstd/expected/compression_zstd.out

@@ -5,23 +5,23 @@ HINT:  The 'DISTRIBUTED BY' clause determines the distribution of data. Make sur
 INSERT INTO zstdtest SELECT g, 'foo' || g FROM generate_series(1, 100000) g;
 INSERT INTO zstdtest SELECT g, 'bar' || g FROM generate_series(1, 100000) g;
 -- Check contents, at the beginning of the table and at the end.
-SELECT * FROM zstdtest ORDER BY id LIMIT 5;
+SELECT * FROM zstdtest ORDER BY (id, t) LIMIT 5;
  id |  t   
 ----+------
   1 | bar1
   1 | foo1
-  2 | foo2
   2 | bar2
+  2 | foo2
   3 | bar3
 (5 rows)
 
-SELECT * FROM zstdtest ORDER BY id DESC LIMIT 5;
+SELECT * FROM zstdtest ORDER BY (id, t) DESC LIMIT 5;
    id   |     t     
 --------+-----------
- 100000 | bar100000
  100000 | foo100000
-  99999 | bar99999
+ 100000 | bar100000
   99999 | foo99999
+  99999 | bar99999
   99998 | foo99998
 (5 rows)
 
@@ -37,46 +37,46 @@ NOTICE:  Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'id' a
 HINT:  The 'DISTRIBUTED BY' clause determines the distribution of data. Make sure column(s) chosen are the optimal data distribution key to minimize skew.
 INSERT INTO zstdtest_1 SELECT g, 'foo' || g FROM generate_series(1, 10000) g;
 INSERT INTO zstdtest_1 SELECT g, 'bar' || g FROM generate_series(1, 10000) g;
-SELECT * FROM zstdtest_1 ORDER BY id LIMIT 5;
+SELECT * FROM zstdtest_1 ORDER BY (id, t) LIMIT 5;
  id |  t   
 ----+------
   1 | bar1
   1 | foo1
-  2 | foo2
   2 | bar2
+  2 | foo2
   3 | bar3
 (5 rows)
 
-SELECT * FROM zstdtest_1 ORDER BY id DESC LIMIT 5;
+SELECT * FROM zstdtest_1 ORDER BY (id, t) DESC LIMIT 5;
   id   |    t     
 -------+----------
  10000 | foo10000
  10000 | bar10000
-  9999 | bar9999
   9999 | foo9999
-  9998 | bar9998
+  9999 | bar9999
+  9998 | foo9998
 (5 rows)
 
 INSERT INTO zstdtest_19 SELECT g, 'foo' || g FROM generate_series(1, 10000) g;
 INSERT INTO zstdtest_19 SELECT g, 'bar' || g FROM generate_series(1, 10000) g;
-SELECT * FROM zstdtest_19 ORDER BY id LIMIT 5;
+SELECT * FROM zstdtest_19 ORDER BY (id, t) LIMIT 5;
  id |  t   
 ----+------
   1 | bar1
   1 | foo1
-  2 | foo2
   2 | bar2
+  2 | foo2
   3 | bar3
 (5 rows)
 
-SELECT * FROM zstdtest_19 ORDER BY id DESC LIMIT 5;
+SELECT * FROM zstdtest_19 ORDER BY (id, t) DESC LIMIT 5;
   id   |    t     
 -------+----------
  10000 | foo10000
  10000 | bar10000
-  9999 | bar9999
   9999 | foo9999
-  9998 | bar9998
+  9999 | bar9999
+  9998 | foo9998
 (5 rows)
 
 -- Test the bounds of compresslevel. None of these are allowed.

gpcontrib/zstd/sql/compression_zstd.sql

@@ -6,8 +6,8 @@ INSERT INTO zstdtest SELECT g, 'foo' || g FROM generate_series(1, 100000) g;
 INSERT INTO zstdtest SELECT g, 'bar' || g FROM generate_series(1, 100000) g;
 
 -- Check contents, at the beginning of the table and at the end.
-SELECT * FROM zstdtest ORDER BY id LIMIT 5;
-SELECT * FROM zstdtest ORDER BY id DESC LIMIT 5;
+SELECT * FROM zstdtest ORDER BY (id, t) LIMIT 5;
+SELECT * FROM zstdtest ORDER BY (id, t) DESC LIMIT 5;
 
 
 -- Test different compression levels:
@@ -17,13 +17,13 @@ CREATE TABLE zstdtest_19 (id int4, t text) WITH (appendonly=true, compresstype=z
 
 INSERT INTO zstdtest_1 SELECT g, 'foo' || g FROM generate_series(1, 10000) g;
 INSERT INTO zstdtest_1 SELECT g, 'bar' || g FROM generate_series(1, 10000) g;
-SELECT * FROM zstdtest_1 ORDER BY id LIMIT 5;
-SELECT * FROM zstdtest_1 ORDER BY id DESC LIMIT 5;
+SELECT * FROM zstdtest_1 ORDER BY (id, t) LIMIT 5;
+SELECT * FROM zstdtest_1 ORDER BY (id, t) DESC LIMIT 5;
 
 INSERT INTO zstdtest_19 SELECT g, 'foo' || g FROM generate_series(1, 10000) g;
 INSERT INTO zstdtest_19 SELECT g, 'bar' || g FROM generate_series(1, 10000) g;
-SELECT * FROM zstdtest_19 ORDER BY id LIMIT 5;
-SELECT * FROM zstdtest_19 ORDER BY id DESC LIMIT 5;
+SELECT * FROM zstdtest_19 ORDER BY (id, t) LIMIT 5;
+SELECT * FROM zstdtest_19 ORDER BY (id, t) DESC LIMIT 5;
 
 
 -- Test the bounds of compresslevel. None of these are allowed.