Make compression.sql regression test independent of default.

This test will fail in "make installcheck" if the installation's
default_toast_compression setting is not 'pglz'.  Make it robust
against that situation.

Dilip Kumar

Discussion: https://postgr.es/m/CAFiTN-t0w+Rc2U3S+y=7KWcLuOYNB5MfWeGdNa7+pg0UovVdcQ@mail.gmail.com

src/test/regress/expected/compression.out

 \set HIDE_TOAST_COMPRESSION false
+-- ensure we get stable results regardless of installation's default
+SET default_toast_compression = 'pglz';
 -- test creating table with compression method
 CREATE TABLE cmdata(f1 text COMPRESSION pglz);
 CREATE INDEX idx ON cmdata(f1);
@@ -245,6 +247,7 @@ CREATE TABLE cmdata2 (f1 text);
 --------+------+-----------+----------+---------+----------+-------------+--------------+-------------
  f1     | text |           |          |         | extended | lz4         |              | 
 
+SET default_toast_compression = 'pglz';
 -- test alter compression method
 ALTER TABLE cmdata ALTER COLUMN f1 SET COMPRESSION lz4;
 INSERT INTO cmdata VALUES (repeat('123456789', 4004));

src/test/regress/expected/compression_1.out

 \set HIDE_TOAST_COMPRESSION false
+-- ensure we get stable results regardless of installation's default
+SET default_toast_compression = 'pglz';
 -- test creating table with compression method
 CREATE TABLE cmdata(f1 text COMPRESSION pglz);
 CREATE INDEX idx ON cmdata(f1);
@@ -241,6 +243,7 @@ CREATE TABLE cmdata2 (f1 text);
 --------+------+-----------+----------+---------+----------+-------------+--------------+-------------
  f1     | text |           |          |         | extended | pglz        |              | 
 
+SET default_toast_compression = 'pglz';
 -- test alter compression method
 ALTER TABLE cmdata ALTER COLUMN f1 SET COMPRESSION lz4;
 ERROR:  unsupported LZ4 compression method

src/test/regress/sql/compression.sql

 \set HIDE_TOAST_COMPRESSION false
 
+-- ensure we get stable results regardless of installation's default
+SET default_toast_compression = 'pglz';
+
 -- test creating table with compression method
 CREATE TABLE cmdata(f1 text COMPRESSION pglz);
 CREATE INDEX idx ON cmdata(f1);
@@ -100,6 +103,7 @@ SET default_toast_compression = 'lz4';
 DROP TABLE cmdata2;
 CREATE TABLE cmdata2 (f1 text);
 \d+ cmdata2
+SET default_toast_compression = 'pglz';
 
 -- test alter compression method
 ALTER TABLE cmdata ALTER COLUMN f1 SET COMPRESSION lz4;