This module provides the functionality required to access and manipulate data stored in a PostgreSQL database.
Add the PostgreSQL driver as a dependency to the Ballerina project.
ballerinax/postgresqlsupports PostgrSQL driver versions above 42.2.18.
You can achieve this by importing the
ballerinax/postgresql.driver package bundles the latest PostgreSQL driver JAR.
Tip: GraalVM native build is supported when
ballerinax/postgresqlis used along with the
If you want to add a PostgreSQL driver of a specific version, you can add it as a dependency in Ballerina.toml. Follow one of the following ways to add the JAR in the file:
Download the JAR and update the path
Add JAR with a maven dependency params
To access a database, you must first create a
The examples for creating a PostgreSQL client can be found below.
Tip: The client should be used throughout the application lifetime.
Create a client
This example shows the different methods of creating a
When the database is in the default username, the client can be created with an empty constructor, and thereby, the client will be initialized with the default properties.
postgresql:Client receives the host, username, password, database, and port. Since the properties are passed in the same order as they are defined
postgresql:Client, you can pass them without named parameters.
In the sample below, the
postgresql:Client uses named parameters to pass the attributes since it is skipping some parameters in the constructor.
property is passed to configure the connection timeout in the PostgreSQL client.
Similarly in the sample below, the
postgresql:Client uses named parameters and it provides an unshared connection pool of the type of
to be used within the client.
For more details about connection pooling, see the
To connect to the PostgreSQL server using an SSL connection, you must add the SSL configurations to the
postgresql:Options when creating the
For the SSL Mode, you can select one of the following modes:
postgresql:VERIFY_IDENTITY according to the requirement.
The key files must be provided in the
Connection pool handling
All database modules share the same connection pooling concept and there are three possible scenarios for
connection pool handling. For its properties and possible values, see the
Note: Connection pooling is used to optimize opening and closing connections to the database. However, the pool comes with an overhead. It is best to configure the connection pool properties as per the application need to get the best performance.
Global, shareable, default connection pool
If you do not provide the
connectionPoolfield when creating the database client, a globally-shareable pool will be created for your database unless a connection pool matching with the properties you provided already exists.
Client-owned, unsharable connection pool
If you define the
connectionPoolfield inline when creating the client with the
sql:ConnectionPooltype, an unsharable connection pool will be created.
Local, shareable connection pool
If you create a record of the
sql:ConnectionPooltype and reuse that in the configuration of multiple clients, for each set of clients that connects to the same database instance with the same set of properties, a shared connection pool will be used.
For more details about each property, see the
sql:Client and all the operations
defined by the
sql:Client will be supported by the
postgresql:Client as well.
Close the client
Once all the database operations are performed, you can close the client you have created by invoking the
operation. This will close the corresponding connection pool if it is not shared by any other database clients.
Note: The client must be closed only at the end of the application lifetime (or closed for graceful stops in a service).
Once the client is created, database operations can be executed through that client. This module defines the interface and common properties that are shared among multiple database clients. It also supports querying, inserting, deleting, updating, and batch updating data.
sql:ParameterizedQuery is used to construct the SQL query to be executed by the client.
You can create a query with constant or dynamic input data as follows.
Query with constant values
Query with dynamic values
Moreover, the SQL package has
sql:arrayFlattenQuery() util functions which make it easier
to create a dynamic/constant complex query.
sql:queryConcat() is used to create a single parameterized query by concatenating a set of parameterized queries.
The sample below shows how to concatenate queries.
A query with the
IN operator can be created using the
sql:ParameterizedQuery as shown below. Here you need to flatten the array and pass each element separated by a comma.
sql:arrayFlattenQuery() util function is used to make the array flattening easier. It makes the inclusion of varying array elements into the query easier by flattening the array to return a parameterized query. You can construct the complex dynamic query with the
IN operator by using both functions as shown below.
This sample creates a table with three columns. The first column is a primary key of type
while the second column is of type
int and the other is of type
CREATE statement is executed via the
execute remote method of the client.
These samples show the data insertion by executing an
INSERT statement using the
execute remote method
of the client.
In this sample, the query parameter values are passed directly into the query statement of the
In this sample, the parameter values, which are assigned to local variables are used to parameterize the SQL query in
execute remote method. This type of parameterized SQL query can be used with any primitive Ballerina type
boolean and in that case, the corresponding SQL type of the parameter is derived
from the type of the Ballerina variable that is passed.
In this sample, the parameter values are passed as an
sql:TypedValue to the
execute remote method. Use the
corresponding subtype of the
sql:TypedValue such as
sql:IntegerValue, etc., when you need to
provide more details such as the exact SQL type of the parameter.
Insert data with auto-generated keys
This sample demonstrates inserting data while returning the auto-generated keys. It achieves this by using the
execute remote method to execute the
These samples show how to demonstrate the different usages of the
query operation to query the
database table and obtain the results as a stream.
Note: When processing the stream, make sure to consume all fetched data or close the stream.
This sample demonstrates querying data from a table in a database.
First, a type is created to represent the returned result set. This record can be defined as an open or a closed record
according to the requirement. If an open record is defined, the returned stream type will include both defined fields
in the record and additional database columns fetched by the SQL query which are not defined in the record.
Note the mapping of the database column to the returned record's property is case-insensitive if it is defined in the
record (i.e., the
ID column in the result can be mapped to the
id property in the record). Additional column names
are added to the returned record as in the SQL query. If the record is defined as a closed record, only the fields defined in the
record are returned or gives an error when additional columns are present in the SQL query. Next, the
SELECT query is executed
query remote method of the client. Once the query is executed, each data record can be retrieved by iterating through
the result set. The
stream returned by the
SELECT operation holds a pointer to the actual data in the database, and it
loads data from the table only when it is accessed. This stream can be iterated only once.
Defining the return type is optional and you can query the database without providing the result type. Hence, the above sample can be modified as follows with an open record type as the return type. The property name in the open record type will be the same as how the column is defined in the database.
There are situations in which you may not want to iterate through the database and in that case, you may decide
to use the
queryRow() operation. If the provided return type is a record, this method returns only the first row
retrieved by the query as a record.
queryRow() operation can also be used to retrieve a single value from the database (e.g., when querying using
COUNT() and other SQL aggregation functions). If the provided return type is not a record (i.e., a primitive data type)
, this operation will return the value of the first column of the first row retrieved by the query.
This sample demonstrates modifying data by executing an
UPDATE statement via the
execute remote method of
This sample demonstrates deleting data by executing a
DELETE statement via the
execute remote method of
Batch update data
This sample demonstrates how to insert multiple records with a single
INSERT statement that is executed via the
batchExecute remote method of the client. This is done by creating a
table with multiple records and
parameterized SQL query as same as the above
Execute stored procedures
This sample demonstrates how to execute a stored procedure with a single
INSERT statement that is executed via the
call remote method of the client.
Note: Once the results are processed, the
closemethod on the
sql:ProcedureCallResultmust be called.
Note: The default thread pool size used in Ballerina is:
the number of processors available * 2. You can configure the thread pool size by using the