Use LOAD not actual code execution to pull in plpython library.

Commit 866566a690bb9916 is insufficient to prevent dump/reload failures
when using transform modules in a database with both plpython2 and
plpython3 installed.  The reason is that the transform extension scripts
use DO blocks as a mechanism to pull in the libpython library before
creating the transform function.  It's necessary to preload the library
because the dynamic loader won't do it for us on every platform, leading
to "unresolved symbol" failures when the transform library is loaded.
But it's *not* necessary to execute Python code, and doing so will
provoke a multiple-Pythons-are-loaded error even after the preceding
commit.

To fix, use LOAD instead of a DO block.  That requires superuser privilege,
but creation of a C function does anyway.  It also embeds knowledge of
the underlying library name for each PL language; but that's wired into
the initdb-time contents of pg_pltemplate too, so that doesn't seem like
a large problem either.  Note that CREATE TRANSFORM as such doesn't call
the language module at all.

Per a report from Paul Jones.  Back-patch to 9.5 where transform modules
were introduced.

8 files changed, 8 insertions, 8 deletions

diff --git a/contrib/hstore_plperl/hstore_plperl--1.0.sql b/contrib/hstore_plperl/hstore_plperl--1.0.sql
index ea0ad7688d..a4fd7c22db 100644
--- a/contrib/hstore_plperl/hstore_plperl--1.0.sql
+++ b/contrib/hstore_plperl/hstore_plperl--1.0.sql
@@ -1,5 +1,5 @@
 -- make sure the prerequisite libraries are loaded
-DO '' LANGUAGE plperl;
+LOAD 'plperl';
 SELECT NULL::hstore;
 
 
diff --git a/contrib/hstore_plperl/hstore_plperlu--1.0.sql b/contrib/hstore_plperl/hstore_plperlu--1.0.sql
index 46ad35c487..2c2e3e3848 100644
--- a/contrib/hstore_plperl/hstore_plperlu--1.0.sql
+++ b/contrib/hstore_plperl/hstore_plperlu--1.0.sql
@@ -1,5 +1,5 @@
 -- make sure the prerequisite libraries are loaded
-DO '' LANGUAGE plperlu;
+LOAD 'plperl';
 SELECT NULL::hstore;
 
 
diff --git a/contrib/hstore_plpython/hstore_plpython2u--1.0.sql b/contrib/hstore_plpython/hstore_plpython2u--1.0.sql
index c998de51c9..a793dc9c0c 100644
--- a/contrib/hstore_plpython/hstore_plpython2u--1.0.sql
+++ b/contrib/hstore_plpython/hstore_plpython2u--1.0.sql
@@ -1,5 +1,5 @@
 -- make sure the prerequisite libraries are loaded
-DO '1' LANGUAGE plpython2u;
+LOAD 'plpython2';
 SELECT NULL::hstore;
 
 
diff --git a/contrib/hstore_plpython/hstore_plpython3u--1.0.sql b/contrib/hstore_plpython/hstore_plpython3u--1.0.sql
index 61d0e47793..a85c85d4c1 100644
--- a/contrib/hstore_plpython/hstore_plpython3u--1.0.sql
+++ b/contrib/hstore_plpython/hstore_plpython3u--1.0.sql
@@ -1,5 +1,5 @@
 -- make sure the prerequisite libraries are loaded
-DO '1' LANGUAGE plpython3u;
+LOAD 'plpython3';
 SELECT NULL::hstore;
 
 
diff --git a/contrib/hstore_plpython/hstore_plpythonu--1.0.sql b/contrib/hstore_plpython/hstore_plpythonu--1.0.sql
index 6acb97aab9..e2e4721dca 100644
--- a/contrib/hstore_plpython/hstore_plpythonu--1.0.sql
+++ b/contrib/hstore_plpython/hstore_plpythonu--1.0.sql
@@ -1,5 +1,5 @@
 -- make sure the prerequisite libraries are loaded
-DO '1' LANGUAGE plpythonu;
+LOAD 'plpython2';  -- change to plpython3 if that ever becomes the default
 SELECT NULL::hstore;
 
 
diff --git a/contrib/ltree_plpython/ltree_plpython2u--1.0.sql b/contrib/ltree_plpython/ltree_plpython2u--1.0.sql
index 29a12d45a2..f040bd3f56 100644
--- a/contrib/ltree_plpython/ltree_plpython2u--1.0.sql
+++ b/contrib/ltree_plpython/ltree_plpython2u--1.0.sql
@@ -1,5 +1,5 @@
 -- make sure the prerequisite libraries are loaded
-DO '1' LANGUAGE plpython2u;
+LOAD 'plpython2';
 SELECT NULL::ltree;
 
 
diff --git a/contrib/ltree_plpython/ltree_plpython3u--1.0.sql b/contrib/ltree_plpython/ltree_plpython3u--1.0.sql
index 1300a78c66..7afe51f148 100644
--- a/contrib/ltree_plpython/ltree_plpython3u--1.0.sql
+++ b/contrib/ltree_plpython/ltree_plpython3u--1.0.sql
@@ -1,5 +1,5 @@
 -- make sure the prerequisite libraries are loaded
-DO '1' LANGUAGE plpython3u;
+LOAD 'plpython3';
 SELECT NULL::ltree;
 
 
diff --git a/contrib/ltree_plpython/ltree_plpythonu--1.0.sql b/contrib/ltree_plpython/ltree_plpythonu--1.0.sql
index 1d1af28f4e..50f35dd16b 100644
--- a/contrib/ltree_plpython/ltree_plpythonu--1.0.sql
+++ b/contrib/ltree_plpython/ltree_plpythonu--1.0.sql
@@ -1,5 +1,5 @@
 -- make sure the prerequisite libraries are loaded
-DO '1' LANGUAGE plpythonu;
+LOAD 'plpython2';  -- change to plpython3 if that ever becomes the default
 SELECT NULL::ltree;