User:Minooz/PostgreSQL Adapter-nexj/schema-ddl

PostgreSQL Adapter for NexJ - Working Inside Schema 'test'

Working with Database Structure - DDL

CREATING SCHEMA

• List of Files needed to be modified *

src- PostgreSQLSchemaManager.java --- (SchemaBackup) // Extends SQLSchemaManager.java - class for reading, creating and upgrading the database schema

test- PostgreSQLSchemaManagerTest.java // Extends SQLSchemaManagerTest.java

Script - scripts are being processed through SQLDataTest.java

• CREATE TABLE

1- DATA TYPE: data types are changed in appendColumnType() based on each jdbc type's equivalent in PostgreSQL.

• mapping JDBC data types to PostgreSQL data types
• comparison between Postgre and MySQL data types

2- STORAGE ENGINE: In MySQL, the storage engine is set to a transactional safe engine such as InnoDB, whereas PostgreSQL has a single built in engine. So, implementation of appendTableSuffix() in PostgreSQLManager.java was removed

3- CHARACTER SET: In MySQL, the character set should be defined when creating a table. Whereas in PostgreSQL when a database is created, the character set is set to 'UTF8' by default.

4- AUTO INCREMENT: PostgreSQL doesn't support 'auto_increment' as some other databases for a unique identifier column. There are two ways around this, 1- To create a 'sequence', 2- Use SERIAL, which is a macro around 'sequence'. SERIAL is an 'integer' and a 'sequence, with the column default to the sequences next value. As of postgreSQL 7.3, to make a serial column unique, it should be specified as a unique constraint or a primary key. More info @ PostgreSQL Resources

/* MySQL version of creating table script */

create table test.RangeTest(
   id int auto_increment not null, s varchar(1) character set utf8 null, bin varbinary(1) null,
   n int null, n1 tinyint unsigned null, l bigint null, "DEC" decimal(10,5) null,
   f float null, d double null, tm datetime null, b boolean null,
   constraint RangeTest_PK primary key(id)
)engine=InnoDB character set = utf8

/* PostgreSQL version of creating table script */

CREATE TABLE test.RangeTest(
   id serial not null, s text null, bin bytea null,
   n integer null, n1 smallint null, l bigint null, "DEC" decimal(10,5) null,
   f double precision null, d double precision null, tm timestamp null, b boolean null,
   constraint RangeTest_PK primary key(id)
);
// Using SERIAL is another way to work around 'sequence'
//CREATE SEQUENCE test.RangeTest_id_seq;
//ALTER TABLE test.RangeTest ALTER COLUMN id SET DEFAULT NEXTVAL('test.RangeTest_id_seq');

• CREATE TEXT TABLE

The implementation in crateTextTable() is removed for now (base class's version is being called).

TODO To be checked if it's the case for PostgreSQL as well.

• CREATE INDEX

The implementation in createIndex() is removed for now (base class's version is being called).

TODO To be checked if it's the case for PostgreSQL as well.

Note- If there was a complain for duplicate index name, a fully qualified name can be used. Just note that PostgreSQL doesn't like fully qualified name as table.indexname for indexes or triggers, instead a '_' can be used: table_indexname

• CREATE Trigger

TODO To be checked if triggers are needed for PostgreSQL as well. It's not an abstract method in SQLSchemaManager.java.

createTrigger() is added to MySQLSchemaManager.java

UPDGRADING SCHEMA

• List of Files needed to be modified

src - PostgreSQLSchemaManager.java --- (SchemaBackup) // Extends SQLSchemaManager.java - class for reading, creating and upgrading the database schema

main.upgrade

test- PostgreSQLSchemaManagerTest.java // Extends SQLSchemaManagerTest.java

Script - postgresql_drop.sql

• DROP TABLE

• INSERT INTO TABLE

• ALTER TABLE