ballerina/sql

Overview

This module provides the common interface and functionality to interact with a database. The corresponding database clients can be created by using specific database modules such as mysql or using the Java Database Connectivity module jdbc.

List of Database Modules

Ballerina now has the jdbc module as the generic DB connector module to connect to any relational database by simply providing the JDBC URL and the other related properties. Ballerina also provides specially designed various database-specific DB connectors so that you can work with different databases and you can access their DB-specific functionalities.

Client

The database client should be created using any of the above-listed database modules and once it is created, the operations and functionality explained below can be used.

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 sql:ConnectionPool.

  1. Global, shareable, default connection pool

    If you do not provide the poolOptions field 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. The JDBC module example below shows how the global connection pool is used.

    1jdbc:Client|sql:Error dbClient =
    2 new ("jdbc:mysql://localhost:3306/testdb",
    3 "root", "root");
  2. Client-owned, unsharable connection pool

    If you define the connectionPool field inline when creating the database client with the sql:ConnectionPool type, an unsharable connection pool will be created. The JDBC module example below shows how the global connection pool is used.

    1jdbc:Client|sql:Error dbClient =
    2 new (url = "jdbc:mysql://localhost:3306/testdb",
    3 connectionPool = { maxOpenConnections: 5 });
  3. Local, shareable connection pool

    If you create a record of the sql:ConnectionPool type 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 created. The JDBC module example below shows how the global connection pool is used.

    1sql:ConnectionPool connPool = {maxOpenConnections: 5};
    2
    3jdbc:Client|sql:Error dbClient1 =
    4 new (url = "jdbc:mysql://localhost:3306/testdb",
    5 connectionPool = connPool);
    6jdbc:Client|sql:Error dbClient2 =
    7 new (url = "jdbc:mysql://localhost:3306/testdb",
    8 connectionPool = connPool);
    9jdbc:Client|sql:Error dbClient3 =
    10 new (url = "jdbc:mysql://localhost:3306/testdb",
    11 connectionPool = connPool);

Closing the Client

Once all the database operations are performed, you can close the database client you have created by invoking the close() operation. This will close the corresponding connection pool if it is not shared by any other database clients.

1error? e = dbClient.close();

Or

1check dbClient.close();

Database Operations

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.

Creating Tables

This sample creates a table with two columns. One column is of type int and the other is of type varchar. The CREATE statement is executed via the execute remote function of the client.

1// Create the ‘Students’ table with the ‘id’, 'name', and ‘age’ fields.
2sql:ExecutionResult ret = check dbClient->execute("CREATE TABLE student(id INT AUTO_INCREMENT, " +
3 "age INT, name VARCHAR(255), PRIMARY KEY (id))");
4//A value of the sql:ExecutionResult type is returned for 'ret'.

Inserting Data

This sample shows three examples of data insertion by executing an INSERT statement using the execute remote function of the client.

In the first example, the query parameter values are passed directly into the query statement of the execute remote function.

1sql:ExecutionResult ret = check dbClient->execute("INSERT INTO student(age, name) " +
2 "values (23, 'john')");

In the second example, the parameter values, which are in local variables are used to parameterize the SQL query in the execute remote function. This type of a parameterized SQL query can be used with any primitive Ballerina type like string, int, float, or 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.

1string name = "Anne";
2int age = 8;
3
4sql:ParameterizedQuery query = `INSERT INTO student(age, name)
5 values (${age}, ${name})`;
6sql:ExecutionResult ret = check dbClient->execute(query);

In the third example, the parameter values are passed as a sql:TypedValue to the execute remote function. Use the corresponding subtype of the sql:TypedValue such as sql:Varchar, sql:Char, sql:Integer, etc., when you need to provide more details such as the exact SQL type of the parameter.

1sql:VarcharValue name = new ("James");
2sql:IntegerValue age = new (10);
3
4sql:ParameterizedQuery query = `INSERT INTO student(age, name)
5 values (${age}, ${name})`;
6sql:ExecutionResult ret = check dbClient->execute(query);

Inserting Data With Auto-generated Keys

This example demonstrates inserting data while returning the auto-generated keys. It achieves this by using the execute remote function to execute the INSERT statement.

1int age = 31;
2string name = "Kate";
3
4sql:ParameterizedQuery query = `INSERT INTO student(age, name)
5 values (${age}, ${name})`;
6sql:ExecutionResultret = check dbClient->execute(query);
7//Number of rows affected by the execution of the query.
8int? count = ret.affectedRowCount;
9//The integer or string generated by the database in response to a query execution.
10string|int? generatedKey = ret.lastInsertId;
11}

Querying Data

This sample shows three examples to demonstrate the different usages of the query operation to query the database table and obtain the results.

This example demonstrates querying data from a table in a database. First, a type is created to represent the returned result set. Note the mapping of the database column to the returned record's property is case-insensitive (i.e., the ID column in the result can be mapped to the id property in the record). Next, the SELECT query is executed via the query remote function of the client by passing that result set type. Once the query is executed, each data record can be retrieved by looping 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.

1// Define a type to represent the results.
2type Student record {
3 int id;
4 int age;
5 string name;
6};
7
8// Select the data from the database table. The query parameters are passed
9// directly. Similar to the `execute` examples, parameters can be passed as
10// sub types of `sql:TypedValue` as well.
11int id = 10;
12int age = 12;
13sql:ParameterizedQuery query = `SELECT * FROM students
14 WHERE id < ${id} AND age > ${age}`;
15stream<Student, sql:Error> resultStream =
16 <stream<Student, sql:Error>> dbClient->query(query, Student);
17
18// Iterating the returned table.
19error? e = resultStream.forEach(function(Student student) {
20 //Can perform any operations using 'student' and can access any fields in the returned record of type Student.
21});

Defining the return type is optional and you can query the database without providing the result type. Hence, the above example 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.

1// Select the data from the database table. The query parameters are passed
2// directly. Similar to the `execute` examples, parameters can be passed as
3// sub types of `sql:TypedValue` as well.
4int id = 10;
5int age = 12;
6sql:ParameterizedQuery query = `SELECT * FROM students
7 WHERE id < ${id} AND age > ${age}`;
8stream<record{}, sql:Error> resultStream = dbClient->query(query);
9
10// Iterating the returned table.
11error? e = resultStream.forEach(function(record{} student) {
12 //Can perform any operations using the 'student' and can access any fields in the returned record.
13});

There are situations in which you may not want to iterate through the database and in that case, you may decide to only use the next() operation in the result stream and retrieve the first record. In such cases, the returned result stream will not be closed, and you have to explicitly invoke the close operation on the sql:Client to release the connection resources and avoid a connection leak as shown below.

1stream<record{}, sql:Error> resultStream =
2 dbClient->query("SELECT count(*) as total FROM students");
3
4record {|record {} value;|}|error? result = resultStream.next();
5
6if result is record {|record {} value;|} {
7 // A valid result is returned.
8} else if result is error {
9 // An error is returned as the result.
10} else {
11 // Student table must be empty.
12}
13
14error? e = resultStream.close();

Updating Data

This example demonstrates modifying data by executing an UPDATE statement via the execute remote function of the client.

1int age = 23;
2sql:ParameterizedQuery query = `UPDATE students SET name = 'John'
3 WHERE age = ${age}`;
4sql:ExecutionResult|sql:Error ret = check dbClient->execute(query);

Deleting Data

This example demonstrates deleting data by executing a DELETE statement via the execute remote function of the client.

1string name = "John";
2sql:ParameterizedQuery query = `DELETE from students WHERE name = ${name}`;
3sql:ExecutionResult|sql:Error ret = check dbClient->execute(query);

Batch Updating Data

This example demonstrates how to insert multiple records with a single INSERT statement that is executed via the batchExecute remote function of the client. This is done by creating a table with multiple records and parameterized SQL query as same as the above execute operations.

1// Create the table with the records that need to be inserted.
2var data = [
3 { name: "John", age: 25 },
4 { name: "Peter", age: 24 },
5 { name: "jane", age: 22 }
6];
7
8// Do the batch update by passing the batches.
9sql:ParameterizedQuery[] batch = from var row in data
10 select `INSERT INTO students ('name', 'age')
11 VALUES (${row.name}, ${row.age})`;
12sql:ExecutionResult[] ret = check dbClient->batchExecute(batch);

Execute SQL Stored Procedures

This example demonstrates how to execute a stored procedure with a single INSERT statement that is executed via the call remote function of the client.

1int uid = 10;
2sql:IntegerOutParameter insertId = new;
3
4sql:ProcedureCallResult|sql:Error ret = dbClient->call(`call InsertPerson(${uid}, ${insertId})`);
5if ret is error {
6 //An error returned.
7} else {
8 stream<record{}, sql:Error>? resultStr = ret.queryResult;
9 if resultStr is stream<record{}, sql:Error> {
10 sql:Error? e = resultStr.forEach(function(record{} result) {
11 //can perform operations using 'result'.
12 });
13 }
14 check ret.close();
15}

Note that you have to invoke the close operation explicitly on the sql:ProcedureCallResult to release the connection resources and avoid a connection leak as shown above.

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 BALLERINA_MAX_POOL_SIZE environment variable.

Functions

[2]

generateApplicationErrorStream
getGlobalConnectionPool

Classes

[81]

ArrayOutParameter

Represents Array Out Parameter used in procedure calls

ArrayValue
D

Represents ArrayValue SQL field.

BigIntArrayValue

Represents BigInt array SQL field.

BigIntOutParameter

Represents BigInt Out Parameter used in procedure calls

BigIntValue

Represents BigInt SQL field.

BinaryArrayValue

Represents Boolean array SQL field.

BinaryOutParameter

Represents Binary Out Parameter used in procedure calls

BinaryValue

Represents Binary SQL field.

BitArrayValue

Represents Bit array SQL field.

BitOutParameter

Represents Bit Out Parameter used in procedure calls

BitValue

Represents Bit SQL field.

BlobOutParameter

Represents Blob Out Parameter used in procedure calls

BlobValue

Represents Blob SQL field.

BooleanArrayValue

Represents Boolean array SQL field.

BooleanOutParameter

Represents Boolean Out Parameter used in procedure calls

BooleanValue

Represents Boolean SQL field.

CharArrayValue

Represents Char array SQL field.

CharOutParameter

Represents Char Out Parameter used in procedure calls

CharValue

Represents Char SQL field.

ClobOutParameter

Represents Clob Out Parameter used in procedure calls

ClobValue

Represents Clob SQL field.

DateArrayValue

Represents Date array SQL field.

DateOutParameter

Represents Date Out Parameter used in procedure calls

DateTimeArrayValue

Represents DateTime array SQL field.

DateTimeOutParameter

Represents DateTime Out Parameter used in procedure calls

DateTimeValue

Represents DateTime SQL field.

DateValue

Represents Date SQL field.

DecimalArrayValue

Represents Decimal array SQL field.

DecimalOutParameter

Represents Decimal Out Parameter used in procedure calls

DecimalValue

Represents Decimal SQL field.

DoubleArrayValue

Represents Double array SQL field.

DoubleOutParameter

Represents Double Out Parameter used in procedure calls

DoubleValue

Represents Double SQL field.

FloatArrayValue

Represents Float array SQL field.

FloatOutParameter

Represents Float Out Parameter used in procedure calls

FloatValue

Represents Float SQL field.

InOutParameter

Represents SQL InOutParameter used in procedure calls.

IntegerArrayValue

Represents Integer array SQL field.

IntegerOutParameter

Represents Integer Out Parameter used in procedure calls

IntegerValue

Represents Integer SQL field.

NCharOutParameter

Represents NChar Out Parameter used in procedure calls

NCharValue

Represents NChar SQL field.

NClobOutParameter

Represents NClob Out Parameter used in procedure calls

NClobValue

Represents NClob SQL field.

NumericArrayValue

Represents Numeric array SQL field.

NumericOutParameter

Represents Numeric Out Parameter used in procedure calls

NumericValue

Represents Numeric SQL field.

NVarcharArrayValue

Represents Varchar NVarchar SQL field.

NVarcharOutParameter

Represents NVarchar Out Parameter used in procedure calls

NVarcharValue

Represents NVarchar SQL field.

ProcedureCallResult

Object that is used to return stored procedure call results.

RealArrayValue

Represents Real array SQL field.

RealOutParameter

Represents Real Out Parameter used in procedure calls

RealValue

Represents Real SQL field.

RefOutParameter

Represents Ref Out Parameter used in procedure calls

RefValue

Represents Ref SQL field.

ResultIterator

The result iterator object that is used to iterate through the results in the event stream.

RowOutParameter

Represents Row Out Parameter used in procedure calls

RowValue

Represents Row SQL field.

SmallIntArrayValue

Represents SmallInt array SQL field.

SmallIntOutParameter

Represents SmallInt Out Parameter used in procedure calls

SmallIntValue

Represents SmallInt SQL field.

StructOutParameter

Represents Struct Out Parameter used in procedure calls

StructValue

Represents Struct SQL field.

TextOutParameter

Represents Text Out Parameter used in procedure calls

TextValue

Represents Text SQL field.

TimeArrayValue

Represents Time array SQL field.

TimeOutParameter

Represents Time Out Parameter used in procedure calls

TimestampArrayValue

Represents Timestamp array SQL field.

TimestampOutParameter

Represents Timestamp Out Parameter used in procedure calls

TimestampValue

Represents Timestamp SQL field.

TimestampWithTimezoneOutParameter

Represents Timestamp with Timezone Out Parameter used in procedure calls

TimeValue

Represents Time SQL field.

TimeWithTimezoneOutParameter

Represents Time With Timezone Out Parameter used in procedure calls

VarBinaryArrayValue

Represents Boolean array SQL field.

VarBinaryOutParameter

Represents VarBinary Out Parameter used in procedure calls

VarBinaryValue

Represents VarBinary SQL field.

VarcharArrayValue

Represents Varchar array SQL field.

VarcharOutParameter

Represents Varchar Out Parameter used in procedure calls

VarcharValue

Represents Varchar SQL field.

XMLOutParameter

Represents XML Out Parameter used in procedure calls

Object Types

[6]

Client

Represents a SQL client.

CustomResultIterator

The object type that is used as a structure to define a custom class with custom implementations for nextResult and getNextQueryResult in the connector modules.

OutParameter

Represents all OUT parameters used in SQL stored procedure call.

ParameterizedCallQuery

Represents Parameterized Call SQL Statement.

ParameterizedQuery

Represents Parameterized SQL query.

TypedValue

Represents a parameter for the SQL Client remote functions when a variable needs to be passed to the remote function.

Records

[4]

BatchExecuteErrorDetail

Represents the properties belonging to an sql:BatchExecuteError.

ConnectionPool

Represents the properties which are used to configure DB connection pool.

DatabaseErrorDetail

Represents the properties belonging to an sql:DatabaseError.

ExecutionResult

The result of the query without returning the rows.

Constants

[2]

EXECUTION_FAILED

Constant indicating that the specific batch statement failed.

SUCCESS_NO_INFO

Constant indicating that the specific batch statement executed successfully but that no count of the number of rows it affected is available.

Types

[4]

BatchExecuteError

Represents an error occurred when a batch execution is running.

DatabaseError

Represents an error caused by an issue related to database accessibility, erroneous queries, constraint violations, database resource clean-up, and other similar scenarios.

Parameter

Represents all parameters used in SQL stored procedure call.

Value

Possible type of parameters that can be passed into the SQL query.

Errors

[2]

ApplicationError

Represents an error originating from application-level causes.

Error

Defines the common error type for the module.