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This PostgreSQL Primer is by no means a replacement for the excellent PostgreSQL documentation.

The goal of this primer is to provide a starting point for the most common actions for working with PostgreSQL, with pointers to more in-depth documentation where applicable.   

In This Chapter

Servoy & PostgreSQL

As of Servoy 5.2 Servoy comes bundled with PostgreSQL. While Servoy comes bundled with PostgreSQL, Servoy is 100% database agnostic. The PostgreSQL database can therefor be replaced by any type of database. 

Bundled PostgreSQL version

Which version of PostgreSQL is shipped with a specific version of Servoy can be found in the Servoy documentation for the specific Servoy version. For the latest version, see the Servoy Stack Info here.

Installing PostgreSQL

As of Servoy 5.2 Servoy comes bundles with PostgreSQL. When selecting the Database option in the All-In-One installer, PostgreSQL is automatically installed and Servoy is setup to connect to it. 

As of Servoy 6.0 the Servoy All-In-One installer provides 2 different options to install PostgreSQL:

When using Servoy 5.2, the EnterpriseDB PostgreSQL Standard Server installer can be manually downloaded from the EnterpriseDB website here.

Embedded PostgreSQL database engine

Compared to the EnterpriseDB PostgreSQL Standard Server the embedded PostgreSQL database engine is a no frills PostgreSQL installation, just just the bare minimal options installed to run, backup and upgrade the PostgreSQL database. 

The PostgreSQL database engine is installed in the ../application_server/postgres_db/ directory. The actual databases and configuration files are stored in the ../application_server/database/ directory. As of Servoy 6.0, the location of the database engine and database files can be configured during installation.

EnterpriseDB PostgreSQL Standard Server

The Standard Server offering of EnterpriseDb adds to enterprise level tools to PostgreSQL, like replication. Besides that the Standard Server installer is more sophisticated than the Servoy installer. It will for example install the PostgreSQL database under it's own user.

Which installation to choose

For production purposes, it's advised to use the EnterpriseDb Standard Server installer. For development and test purposes, both the embedded PostgreSQL database  engine and the EnterpriseDB option would be sufficient.

Upgrading PostgreSQL

Embedded PostgreSQL database engine

To be described

EnterpriseDB installation

Upgrading an EnterpriseDB Standard Server installation to the next maintenance release, lets say 9.0.1 to 9.0.2, can be done by running the 9.0.2 installer. It will automatically find the 9.0.1 installation and update it. Make sure to stop Servoy (and any other client connecting to PostgreSQL) performing the upgrade.

Upgrading major or minor versions, lets say from 9.0.2 to 9.1 is not possible in the same manner. Running the 9.1 installer will install 9.1 next to the 9.0 installation. The installer automatically set the port of this version to one that doesn't collide with the one already installed. So the 2 versions can run at the same time.

To get the databases over to the new version a backup can be made of the entire database cluster using the command-line pg_dumpall backup utility, after which the backup can be loaded back into the new instance using the psql utility. This operation an also be performed using PgAdmin. It is recommended to use the tools from the newer version to backup the databases from the older version.

See the backup section on this page for more information on how to do backups and restores.

Starting and stopping PostgreSQL manually

Through the pg_ctl tool that comes with PostgreSQL, it is easy to start and stop a PostgreSQL database. In a default installation the  pg_ctl tool is located in

../application_server/postgres_db/bin/

When you have used the EnterpriseDB (EDB) installer then all of PostgreSQL (binary and database cluster) is installed in the following directory:

OSX

/Library/PostgreSQL/9.0/

Windows

C:\Program Files\PostgreSQL\9.0\

Linux

/opt/PostgreSQL/9.0/

Where the subdirectory bin holds the command-line tools and other binaries and the subdirectory data holds the database cluster. Also PostgreSQL will be running under the system user postgres and the data directory is only accesible by that user. All this is for security.

On linux however you can also use ready made packages specially made for the Linux distribution and have their own places of storing the various parts of PostgreSQL.

Starting PostgreSQL

Using the bundled PostgreSQL (assuming you run this from within the application_server directory):

postgres_db\bin\pg_ctl start -D database -l postgres_db\postgres_log.txt

When using the EDB installed version of PostgreSQL then the command is the following:

sudo -u postgres /Library/PostgreSQL/9.0/bin/pg_ctl start -D /Library/PostgreSQL/9.0/data

The EDB installed version already writes logs in the data/pg_log/ directory so no need to add the -l argument.

Stopping PostgreSQL 

Using the bundled PostgreSQL (assuming you run this from within the application_server directory):

postgres_db\bin\pg_ctl stop -D database

When using the EDB installed version of PostgreSQL then the command is the following:

 sudo -u postgres /Library/PostgreSQL/9.0/bin/pg_ctl stop -D /Library/PostgreSQL/9.0/data

You need to provide the location of the database cluster because you could have instances of PostgreSQL running using different data directories.

Running PostgreSQL as a Service

Windows

The pg_ctl utility that comes with PostgreSQL has a built-in command to register the PostgreSQL database as a Windows Service

Registering the Windows Service:

postgres_db\bin\pg_ctl register -N PostgreSQL -D database

Unregistering the Windows Service:

postgres_db\bin\pg_ctl unregister -N PostgreSQL

The commands above assume execution from the ../application_server/ directory. When executing from a different location, make sure to update the paths to the database (-D database).

The -N option specifies the name for the Windows Service. Make sure the name is unique. 

When also running the Servoy Application Server using the Service Component, a dependency can be setup between the Windows Service for the database and the Application Server. See Running the Server As a Service for more information.

OSX

See http://www.postgresql.org/docs/9.0/interactive/server-start.html

*nix

See http://www.postgresql.org/docs/9.0/interactive/server-start.html

Performing backups & restores

PostgreSQL stores it's data in a 'database cluster' which is a collection of files and directories that together make up the entire database. It's not recommended to backup these files, but instead use the backup utilities that come with PostgreSQL.

Manual backups

PostgreSQL provides a pg_dump and a pg_dumpall utility to make a backup file of a running database. In a default installation of Servoy, the utilities are located in ../application_server/postgres_db/bin/. These utilities can be used command-line, but also through the PgAdmin utility.

Backup a specific database

postgres_db\bin\pg_dump -U dba -Fc servoy_repository > servoy_repository.dump

Restore dump into a newly created database

postgres_db\bin\pg_restore -U dba -d new_servoy_repository  servoy_repository.dump

Backup all databases

postgres_db\bin\pg_dumpall -U dba -f db.out

Reload all database dump

postgres_db\bin\psql -U dba -f db.out postgres

Note that the examples above are very minimalistic. The utilities provided by PostgreSQL offer many options. Check the PostgreSQL documentation on pg_dump, pg_dumpall, pg_restore and pg_sql for detailed information.

Also be aware that if you have PostgreSQL running on a non-default port (default is 5432) then you need to add -p <portnr> argument.

All the PostgreSQL command-line tools have an extensive help build in. You can access it by using the --help argument.

The samples above assume execution from the ../application_server/ directory.

PostgreSQL Database Admin tool

For PostgreSQL there are multiple admin tools available, from commercial to open source. The most used admin tool for PostgreSQL is the open source, cross-platform PgAdmin.

PgAdmin can be downloaded here and the excellent documentation is available here.

The EnterpriseDB installer for PostgreSQL has the PgAdmin tool bundled.  

PostgreSQL SQL Tips 'n' Tricks

No automatic type casting

PostgreSQL doesn't do automatic casting of types. This means that when sending in parameters into a prepared statement, it is up to the developer to make sure to send in the right type.

For example:

var value = 1;
var query = 'SELECT * FROM table WHERE textcolumn = ?'
var args = new Array();
args[0] = value;
var dataset = databaseManager.getDataSetByQuery(controller.getServerName(), query, args, maxReturnedRows);

Has to become:

var value = 1;
var query = 'SELECT * FROM table WHERE textcolumn = ?'
var args = new Array();
args[0] = value + ""; //forcing the integer value to become a string
var dataset = databaseManager.getDataSetByQuery(controller.getServerName(), query, args, maxReturnedRows);

Quoting strings and aliases 

In PostgreSQL, the use of quotes and double quotes is more strict than in some other databases.

Quoting for column Aliasses:

SELECT some_column as "A nice name" FROM table

Quoting literal strings:

SELECT * FROM table where text_column = 'someValue'

Migrating to PostgreSQL

A good starting point to data migration towards PostgreSQL is the PostgreSQL wiki, which has a lot of tutorials migrating data into postgreSQL from many different source databases.

When migration an existing solution developed in Servoy from one type of database to PostgreSQL, Servoy's built-in mechanism to generate the required data model in a new database and to move sample data can also be used to migrate to PostgreSQL (or any other type of database). There are however some restrictions. Such a migration will not move views, stored procedures and functions, database level triggers and sequences. If the amount of records to be moved is very large, memory issues can occur due to the sheer amount of data. To make sure that PK-FK integrity stays in tact in import of the sample data, either Servoy Sequences must be used or the database level generation of sequence values (especially for PK sequences) must be temporarily disabled. 

When the amount of data to be moved to the new database is massive or required pre-processing, a better solution is to dump the data to a generic format and import it directly into the new database.

When migrating from Sybase to PostgreSQL, PgExperts provides a special migration service for Servoy customers. For more information on this service check the PgExperts website