Move "username" column to the last position on analysis_catalog - fixes #276

Due to the way it was first implemented, the "username" column would be
on a different position depending on if it was an extension upgrade or
a fresh install.

This caused problems with pg_dumping databases and restoring them.
pg_dump does not include the extension source (so this table's schema is
not included on the dump) but does include this contents, using a COPY
without column names by default and failing due to the order difference.

After this has run, all tables (whether updated or not) will have the
"username" column on the last position.

scripts-available/CDB_AnalysisCatalog.sql

@@ -1,8 +1,6 @@
 -- Table to register analysis nodes from https://github.com/cartodb/camshaft
 CREATE TABLE IF NOT EXISTS
 cartodb.cdb_analysis_catalog (
-    -- useful for multi account deployments
-    username text,
     -- md5 hex hash
     node_id char(40) CONSTRAINT cdb_analysis_catalog_pkey PRIMARY KEY,
     -- being json allows to do queries like analysis_def->>'type' = 'buffer'
@@ -28,7 +26,9 @@ cartodb.cdb_analysis_catalog (
     -- store error message for failures
     last_error_message text,
     -- cached tables involved in the analysis
-    cache_tables regclass[] NOT NULL DEFAULT '{}'
+    cache_tables regclass[] NOT NULL DEFAULT '{}',
+    -- useful for multi account deployments
+    username text
 );
 
 -- This can only be called from an SQL script executed by CREATE EXTENSION
@@ -38,14 +38,9 @@ BEGIN
 END
 $$;
 
-DO $$
-    BEGIN
-        BEGIN
-            ALTER TABLE cartodb.cdb_analysis_catalog ADD COLUMN username text;
-        EXCEPTION
-            WHEN duplicate_column THEN END;
-    END;
-$$;
+-- Migrations to add new columns from old versions.
+-- IMPORTANT: Those columns will be added in order of creation. To be consistent
+-- in column order, ensure that new columns are added at the end and in the same order.
 
 DO $$
     BEGIN
@@ -73,3 +68,28 @@ DO $$
             WHEN duplicate_column THEN END;
     END;
 $$;
+
+DO $$
+    BEGIN
+        BEGIN
+            ALTER TABLE cartodb.cdb_analysis_catalog ADD COLUMN username text;
+        EXCEPTION
+            WHEN duplicate_column THEN END;
+    END;
+$$;
+
+-- We want the "username" column to be moved to the last position if it was on a position from other versions
+-- see https://github.com/CartoDB/cartodb-postgresql/issues/276
+DO LANGUAGE 'plpgsql' $$
+    DECLARE
+        column_index int;
+    BEGIN
+        SELECT ordinal_position FROM information_schema.columns WHERE table_name='cdb_analysis_catalog' AND table_schema='cartodb' AND column_name='username' INTO column_index;
+        IF column_index = 1 OR column_index = 10 THEN
+           ALTER TABLE cartodb.cdb_analysis_catalog ADD COLUMN username_final text;
+           UPDATE cartodb.cdb_analysis_catalog SET username_final = username;
+           ALTER TABLE cartodb.cdb_analysis_catalog DROP COLUMN username;
+           ALTER TABLE cartodb.cdb_analysis_catalog RENAME COLUMN username_final TO username;
+        END IF;
+    END;
+$$;