Postgres producer ALTER COLUMN: specify USING for datatype change

Postgres 8 and later require a C<< USING expression >> clause when
changing the type of a column in a potentially lossy manner, such
as from C<text> to C<numeric>.

This change adds an automatic "USING (colname::datatype)" suffix
any time the data type has changed, which should be a safe default.
It is also conditioned on the version of Postgres, but also makes
it the default in absence of a version, since Pg 8 is so old.

Author: nrdvana

lib/SQL/Translator/Producer/PostgreSQL.pm

@@ -35,6 +35,12 @@ The version of postgres to generate DDL for. Turns on features only available in
 If your postgres_version is higher than 8.003 (I should hope it is by now), then the DDL
 generated for dropping objects in the database will contain IF EXISTS.
 
+=item ALTER COLUMN ... TYPE ... USING
+
+Postgres 8 and later require a C<< USING expression >> clause when changing the type of a column
+in a potentially lossy manner, such as from C<text> to C<numeric>.  This the default when the
+version is undefined, or when set to a number greater or equal to 8.
+
 =back
 
 =item attach_comments
@@ -910,27 +916,31 @@ sub alter_field {
   # rename later
   # BUT: drop geometry is done before the rename, cause it work's on the
   # $from_field directly
+  my $to_table_quoted= $generator->quote($to_field->table->name);
+  my $to_field_quoted= $generator->quote($to_field->name);
   push @out,
       sprintf('ALTER TABLE %s RENAME COLUMN %s TO %s',
-    map($generator->quote($_), $to_field->table->name, $from_field->name, $to_field->name,),)
+        $to_table_quoted, $generator->quote($from_field->name), $to_field_quoted)
       if ($from_field->name ne $to_field->name);
 
   push @out,
       sprintf('ALTER TABLE %s ALTER COLUMN %s SET NOT NULL',
-    map($generator->quote($_), $to_field->table->name, $to_field->name),)
+        $to_table_quoted, $to_field_quoted)
       if (!$to_field->is_nullable and $from_field->is_nullable);
 
   push @out,
       sprintf('ALTER TABLE %s ALTER COLUMN %s DROP NOT NULL',
-    map($generator->quote($_), $to_field->table->name, $to_field->name),)
+        $to_table_quoted, $to_field_quoted)
       if (!$from_field->is_nullable and $to_field->is_nullable);
 
   my $from_dt = convert_datatype($from_field);
   my $to_dt   = convert_datatype($to_field);
-  push @out,
-      sprintf('ALTER TABLE %s ALTER COLUMN %s TYPE %s',
-    map($generator->quote($_), $to_field->table->name, $to_field->name), $to_dt,)
-      if ($to_dt ne $from_dt);
+  push @out, ($options->{postgres_version}//8) < 8
+    ? sprintf('ALTER TABLE %s ALTER COLUMN %s TYPE %s',
+              $to_table_quoted, $to_field_quoted, $to_dt)
+    : sprintf('ALTER TABLE %s ALTER COLUMN %s TYPE %s USING (%s::%s)',
+              $to_table_quoted, $to_field_quoted, $to_dt, $to_field_quoted, $to_dt)
+    if $to_dt ne $from_dt;
 
   my ($from_enum_typename, $from_list) = _enum_typename_and_values($from_field);
   my ($to_enum_typename,   $to_list)   = _enum_typename_and_values($to_field);

t/30sqlt-new-diff-pgsql.t

@@ -72,19 +72,19 @@ DROP INDEX "u_name";
 
 ALTER TABLE "person" ADD COLUMN "is_rock_star" smallint DEFAULT 1;
 
-ALTER TABLE "person" ALTER COLUMN "person_id" TYPE serial;
+ALTER TABLE "person" ALTER COLUMN "person_id" TYPE serial USING ("person_id"::serial);
 
 ALTER TABLE "person" ALTER COLUMN "name" SET NOT NULL;
 
 ALTER TABLE "person" ALTER COLUMN "age" SET DEFAULT 18;
 
 ALTER TABLE "person" ALTER COLUMN "weight" DROP NOT NULL;
 
-ALTER TABLE "person" ALTER COLUMN "iq" TYPE bigint;
+ALTER TABLE "person" ALTER COLUMN "iq" TYPE bigint USING ("iq"::bigint);
 
 ALTER TABLE "person" ALTER COLUMN "nickname" SET NOT NULL;
 
-ALTER TABLE "person" ALTER COLUMN "nickname" TYPE character varying(24);
+ALTER TABLE "person" ALTER COLUMN "nickname" TYPE character varying(24) USING ("nickname"::character varying(24));
 
 ALTER TABLE "person" RENAME COLUMN "description" TO "physical_description";
 
@@ -134,19 +134,19 @@ ALTER TABLE person DROP CONSTRAINT UC_age_name;
 
 ALTER TABLE person ADD COLUMN is_rock_star smallint DEFAULT 1;
 
-ALTER TABLE person ALTER COLUMN person_id TYPE serial;
+ALTER TABLE person ALTER COLUMN person_id TYPE serial USING (person_id::serial);
 
 ALTER TABLE person ALTER COLUMN name SET NOT NULL;
 
 ALTER TABLE person ALTER COLUMN age SET DEFAULT 18;
 
 ALTER TABLE person ALTER COLUMN weight DROP NOT NULL;
 
-ALTER TABLE person ALTER COLUMN iq TYPE bigint;
+ALTER TABLE person ALTER COLUMN iq TYPE bigint USING (iq::bigint);
 
 ALTER TABLE person ALTER COLUMN nickname SET NOT NULL;
 
-ALTER TABLE person ALTER COLUMN nickname TYPE character varying(24);
+ALTER TABLE person ALTER COLUMN nickname TYPE character varying(24) USING (nickname::character varying(24));
 
 ALTER TABLE person RENAME COLUMN description TO physical_description;
 

t/47postgres-producer.t

@@ -264,7 +264,7 @@ subtest 'exclude constraints' => sub {
 my $alter_field = SQL::Translator::Producer::PostgreSQL::alter_field($field1, $field2);
 is(
   $alter_field, qq[ALTER TABLE mytable ALTER COLUMN myfield SET NOT NULL;
-ALTER TABLE mytable ALTER COLUMN myfield TYPE character varying(25)],
+ALTER TABLE mytable ALTER COLUMN myfield TYPE character varying(25) USING (myfield::character varying(25))],
   'Alter field works'
 );
 
@@ -296,7 +296,7 @@ my $alter_field_complex = SQL::Translator::Producer::PostgreSQL::alter_field($fi
 is(
   $alter_field_complex,
   q{ALTER TABLE mytable RENAME COLUMN my_complex_field TO my_altered_field;
-ALTER TABLE mytable ALTER COLUMN my_altered_field TYPE character varying(60);
+ALTER TABLE mytable ALTER COLUMN my_altered_field TYPE character varying(60) USING (my_altered_field::character varying(60));
 ALTER TABLE mytable ALTER COLUMN my_altered_field SET DEFAULT 'whatever'},
   'Complex Alter field works'
 );

t/63-spacial-pgsql.t

@@ -83,15 +83,15 @@ ALTER TABLE "my'table" DROP CONSTRAINT "enforce_dims_myfield";
 ALTER TABLE "my'table" DROP CONSTRAINT "enforce_srid_myfield";
 ALTER TABLE "my'table" DROP CONSTRAINT "enforce_geotype_myfield";
 ALTER TABLE "my'table" ALTER COLUMN "myfield" SET NOT NULL;
-ALTER TABLE "my'table" ALTER COLUMN "myfield" TYPE character varying(25)],
+ALTER TABLE "my'table" ALTER COLUMN "myfield" TYPE character varying(25) USING ("myfield"::character varying(25))],
   'Alter field geometry to non geometry works'
 );
 
 my $alter_field2 = SQL::Translator::Producer::PostgreSQL::alter_field($field2, $field1, $options);
 is(
   $alter_field2,
   qq[ALTER TABLE "my'table" ALTER COLUMN "myfield" DROP NOT NULL;
-ALTER TABLE "my'table" ALTER COLUMN "myfield" TYPE geometry;
+ALTER TABLE "my'table" ALTER COLUMN "myfield" TYPE geometry USING ("myfield"::geometry);
 INSERT INTO geometry_columns VALUES ('','myschema','my''table','myfield','2','-1','POINT');
 ALTER TABLE "my'table" ADD CONSTRAINT "enforce_dims_myfield" CHECK ((ST_NDims("myfield") = 2));
 ALTER TABLE "my'table" ADD CONSTRAINT "enforce_srid_myfield" CHECK ((ST_SRID("myfield") = -1));