= Reactive MSSQL Client
:PREPARED_PARAMS: `@1`, `@2`, etc…​
:batching-unsupported:

The Reactive MSSQL Client is a client for Microsoft SQL Server with a straightforward API focusing on
scalability and low overhead.

*Features*

* Event driven
* Lightweight
* Built-in connection pooling
* Direct memory to object without unnecessary copies
* Java 8 Date and Time

*Not supported yet*

* Prepared queries caching
* Batch and cursor
* Row streaming
* Some https://github.com/eclipse-vertx/vertx-sql-client/issues/608#issuecomment-629390027[data types] are not supported

== Usage

To use the Reactive MSSQL Client add the following dependency to the _dependencies_ section of your build descriptor:

* Maven (in your `pom.xml`):

[source,xml]
----
<dependency>
  <groupId>${maven.groupId}</groupId>
  <artifactId>${maven.artifactId}</artifactId>
  <version>${maven.version}</version>
</dependency>
----
* Gradle (in your `build.gradle` file):

[source,groovy]
----
dependencies {
  compile '${maven.groupId}:${maven.artifactId}:${maven.version}'
}
----

== Getting started

Here is the simplest way to connect, query and disconnect

[source,$lang]
----
{@link examples.MSSQLClientExamples#gettingStarted()}
----

== Connecting to SQL Server

Most of the time you will use a pool to connect to MSSQL:

[source,$lang]
----
{@link examples.MSSQLClientExamples#connecting01}
----

The pooled client uses a connection pool and any operation will borrow a connection from the pool
to execute the operation and release it to the pool.

If you are running with Vert.x you can pass it your Vertx instance:

[source,$lang]
----
{@link examples.MSSQLClientExamples#connecting02}
----

You need to release the pool when you don't need it anymore:

[source,$lang]
----
{@link examples.MSSQLClientExamples#connecting03}
----

When you need to execute several operations on the same connection, you need to use a client
{@link io.vertx.mssqlclient.MSSQLConnection connection}.

You can easily get one from the pool:

[source,$lang]
----
{@link examples.MSSQLClientExamples#connecting04}
----

Once you are done with the connection you must close it to release it to the pool, so it can be reused.

== Configuration

=== Data Object

A simple way to configure the client is to specify a `MSSQLConnectOptions` data object.

[source,$lang]
----
{@link examples.MSSQLClientExamples#configureFromDataObject(io.vertx.core.Vertx)}
----

=== Connection URI

As an alternative to configuring the client with a {@link io.vertx.mssqlclient.MSSQLConnectOptions} data object, you can use a connection URI:

[source,$lang]
----
{@link examples.MSSQLClientExamples#configureFromUri(io.vertx.core.Vertx)}
----

The connection URI format is defined by the client in an idiomatic way: `sqlserver://[user[:[password]]@]host[:port][/database][?attribute1=value1&attribute2=value2...]`

Currently, the client supports the following parameter keywords in connection uri (keys are case-insensitive):

* host
* port
* user
* password
* database

== Connect retries

You can configure the client to retry when a connection fails to be established.

[source,$lang]
----
{@link examples.MSSQLClientExamples#reconnectAttempts}
----

include::queries.adoc[leveloffset=1]

include::connections.adoc[]

include::transactions.adoc[]

== Tracing queries

include::tracing.adoc[]

== Data types supported

Currently, the client supports the following SQL Server types:

* TINYINT(`java.lang.Short`)
* SMALLINT(`java.lang.Short`)
* INT(`java.lang.Integer`)
* BIGINT(`java.lang.Long`)
* BIT(`java.lang.Boolean`)
* REAL(`java.lang.Float`)
* DOUBLE(`java.lang.Double`)
* NUMERIC/DECIMAL(`{@link java.math.BigDecimal}`)
* CHAR/VARCHAR(`java.lang.String`)
* NCHAR/NVARCHAR(`java.lang.String`)
* DATE(`java.time.LocalDate`)
* TIME(`java.time.LocalTime`)
* DATETIME2(`java.time.LocalDateTime`)
* DATETIMEOFFSET(`java.time.OffsetDateTime`)
* BINARY/VARBINARY(`io.vertx.core.buffer.Buffer`)

Tuple decoding uses the above types when storing values.

=== Using Java `enum` types

SQL Server does not have `ENUM` data type, but the client can map the retrieved string/numeric data type to enum.

You can encode Java enums like this:

[source,$lang]
----
{@link examples.MSSQLClientExamples#enumeratedType01Example}
----

You can decode a Java enum like this:

[source,$lang]
----
{@link examples.MSSQLClientExamples#enumeratedType02Example}
----

=== Handling `NULL`

If you modify a `Tuple` with one of the `addXXX` methods, `null` values are handled transparently.

The client can infer the right SQL type when executing a prepared query:

[source,$lang]
----
{@link examples.MSSQLClientExamples#transparentNullHandling}
----

Otherwise, you should declare the type explicitely using one of the {@link io.vertx.sqlclient.data.NullValue} constants or the {@link io.vertx.sqlclient.data.NullValue#of} method:

[source,$lang]
----
{@link examples.MSSQLClientExamples#explicitNullHandling}
----

== Collector queries

You can use Java collectors with the query API:

[source,$lang]
----
{@link examples.MSSQLClientExamples#collector01Example(io.vertx.sqlclient.SqlClient)}
----

The collector processing must not keep a reference on the {@link io.vertx.sqlclient.Row} as
there is a single row used for processing the entire set.

The Java `Collectors` provides many interesting predefined collectors, for example you can
create easily create a string directly from the row set:

[source,$lang]
----
{@link examples.MSSQLClientExamples#collector02Example(io.vertx.sqlclient.SqlClient)}
----
