SingleStoreDB Spark Connector
Version: 4.1.4
Getting Started
You can find the latest version of the connector on Maven Central and
spark-packages.org. The group is com.singlestore
and the artifact is
singlestore-spark-connector_2.11
for Spark 2 and singlestore-spark-connector_2.12
for Spark 3.
You can add the connector to your Spark application using: spark-shell, pyspark, or spark-submit
$SPARK_HOME/bin/spark-shell --packages com.singlestore:singlestore-spark-connector_2.12:4.1.4-spark-3.4.0
We release multiple versions of the singlestore-spark-connector
, one for each supported Spark version.
The connector follows the x.x.x-spark-y.y.y
naming convention, where x.x.x
represents the connector version
and y.y.y
represents the corresponding Spark version.
For example, in connector 4.1.4-spark-3.4.0
, 4.1.4 is the version of the connector,
compiled and tested against Spark version 3.4.0.
It is critical to select the connector version that corresponds to the Spark version in use.
In addition to adding the singlestore-spark-connector
, you will also need to have the
SingleStoreDB JDBC driver installed. This library is tested against the following
SingleStoreDB driver version:
"com.singlestore" % "singlestore-jdbc-client" % "1.1.0"
Once you have everything installed, you're almost ready to run your first queries against SingleStoreDB!
Configuration
The singlestore-spark-connector
is configurable globally via Spark options and
locally when constructing a DataFrame. The options are named the same, however
global options have the prefix spark.datasource.singlestore.
.
Basic options
Option | Default value | Description |
---|---|---|
ddlEndpoint (On-Premise deployment) (required) |
- | The hostname or IP address of the SingleStoreDB Master Aggregator in the host[:port] format, where port is an optional parameter. Example: master-agg.foo.internal:3308 or master-agg.foo.internal . |
dmlEndpoints (On-Premise deployment) |
ddlEndpoint | The hostname or IP address of SingleStoreDB Aggregator nodes to run queries against in the host[:port],host[:port],... format, where :port is an optional parameter (multiple hosts separated by comma). Example: child-agg:3308,child-agg2 . |
clientEndpoint (Cloud deployment) (required) |
- | The hostname or IP address to the SingleStoreDB Cloud workspace to run queries against in the format host[:port] (port is optional). Ex. svc-b093ff56-7d9e-499f-b970-7913852facc4-ddl.aws-oregon-2.svc.singlestore.com:3306 |
user |
root |
The SingleStoreDB username. |
password |
- | Password of the SingleStoreDB user. |
query |
- | The query to run (mutually exclusive with dbtable). |
dbtable |
- | The table to query (mutually exclusive with query). |
database |
- | If set, all connections use the specified database by default. |
Read options
Option | Default value | Description |
---|---|---|
disablePushdown |
false |
Disable SQL Pushdown when running queries. |
enableParallelRead |
automaticLite |
Enables reading data in parallel for some query shapes. It can have of the following values: disabled , automaticLite , automatic , and forced . For more information, see Parallel Read Support. |
parallelRead.Features |
ReadFromAggregators,ReadFromAggregatorsMaterialized |
Specifies a comma separated list of parallel read features that are tried in the order they are listed. We support the following features: ReadFromLeaves , ReadFromAggregators , and ReadFromAggregatorsMaterialized . Example: ReadFromAggregators,ReadFromAggregatorsMaterialized . For more information, see Parallel Read Support. |
parallelRead.tableCreationTimeoutMS |
0 |
Specifies the amount of time (in milliseconds) the reader waits for the result table creation when using the ReadFromAggregators feature. If set to 0 , timeout is disabled. |
parallelRead.tableCreationTimeoutMaterializedMS |
0 |
Specifies the amount of time (in milliseconds) the reader waits for the result table creation when using the ReadFromAggregatorsMaterialized feature. If set to 0 , timeout is disabled. |
parallelRead.maxNumPartitions |
0 |
Specifies the Maximum number of partitions in the resulting DataFrame. If set to 0 , no limit is applied. |
parallelRead.repartition |
false |
Repartition data before reading. |
parallelRead.repartition.columns |
RAND() |
Specifies a comma separated list of columns that are used for repartitioning (when parallelRead.repartition is enabled). By default, an additional column with RAND() value is used for repartitioning. |
Write options
Option | Default value | Description |
---|---|---|
overwriteBehavior |
dropAndCreate |
Specifies the behavior during Overwrite. It can have one of the following values: dropAndCreate , truncate , merge . |
truncate |
false |
overwriteBehavior instead. Truncates instead of dropping an existing table during Overwrite. |
loadDataCompression |
Gzip |
Compresses data on load. It can have one of the following three values: GZip , LZ4 , and Skip . |
loadDataFormat |
CSV |
Serializes data on load. It can have one of the following values: Avro or CSV . |
tableKey |
- | Specifies additional keys to add to tables created by the connector. See Specifying keys for tables created by the Spark Connector for more information. |
onDuplicateKeySQL |
- | If this option is specified and a new row with duplicate PRIMARY KEY or UNIQUE index is inserted, SingleStoreDB performs an UPDATE operation on the existing row. See Inserting rows into the table with ON DUPLICATE KEY UPDATE for more information. |
insertBatchSize |
10000 |
Specifies the size of the batch for row insertion. |
maxErrors |
0 |
The maximum number of errors in a single LOAD DATA request. When this limit is reached, the load fails. If this property is set to 0 , no error limit exists. |
createRowstoreTable |
rowstore |
If enabled, the connector creates a rowstore table. |
Connection pool options
Option | Default value | Description |
---|---|---|
driverConnectionPool.Enabled |
true |
Enables using of connection pool on the driver. (default: true ) |
driverConnectionPool.MaxOpenConns |
-1 |
The maximum number of active connections with the same options that can be allocated from the driver pool at the same time, or negative for no limit. (default: -1 ) |
driverConnectionPool.MaxIdleConns |
8 |
The maximum number of connections with the same options that can remain idle in the driver pool, without extra ones being released, or negative for no limit. (default: 8 ) |
driverConnectionPool.MinEvictableIdleTimeMs |
30000 (30 sec) |
The minimum amount of time an object may sit idle in the driver pool before it is eligible for eviction by the idle object evictor (if any). (default: 30000 - 30 sec) |
driverConnectionPool.TimeBetweenEvictionRunsMS |
1000 (1 sec) |
The number of milliseconds to sleep between runs of the idle object evictor thread on the driver. When non-positive, no idle object evictor thread will be run. (default: 1000 - 1 sec) |
driverConnectionPool.MaxWaitMS |
-1 |
The maximum number of milliseconds that the driver pool will wait (when there are no available connections) for a connection to be returned before throwing an exception, or -1 to wait indefinitely. (default: -1 ) |
driverConnectionPool.MaxConnLifetimeMS |
-1 |
The maximum lifetime in milliseconds of a connection. After this time is exceeded the connection will fail the next activation, passivation, or validation test and wonβt be returned by the driver pool. A value of zero or less means the connection has an infinite lifetime. (default: -1 ) |
executorConnectionPool.Enabled |
true |
Enables using of connection pool on executors. (default: true ) |
executorConnectionPool.MaxOpenConns |
true |
The maximum number of active connections with the same options that can be allocated from the executor pool at the same time, or negative for no limit. (default: true ) |
executorConnectionPool.MaxIdleConns |
8 |
The maximum number of connections with the same options that can remain idle in the executor pool, without extra ones being released, or negative for no limit. (default: 8 ) |
executorConnectionPool.MinEvictableIdleTimeMs |
2000 |
The minimum amount of time an object may sit idle in the executor pool before it is eligible for eviction by the idle object evictor (if any). (default: 2000 - 2 sec) |
executorConnectionPool.TimeBetweenEvictionRunsMS |
1000 |
The number of milliseconds to sleep between runs of the idle object evictor thread on the executor. When non-positive, no idle object evictor thread will be run. (default: 1000 - 1 sec) |
executorConnectionPool.MaxWaitMS |
-1 |
The maximum number of milliseconds that the executor pool will wait (when there are no available connections) for a connection to be returned before throwing an exception, or -1 to wait indefinitely. (default: -1 ) |
executorConnectionPool.MaxConnLifetimeMS |
-1 |
The maximum lifetime in milliseconds of a connection. After this time is exceeded the connection will fail the next activation, passivation, or validation test and wonβt be returned by the executor pool. A value of zero or less means the connection has an infinite lifetime. (default: -1 ) |
Examples
singlestore-spark-connector
for SingleStoreDB Cloud
Configure The following example configures the singlestore-spark-connector
globally:
spark.conf.set("spark.datasource.singlestore.clientEndpoint", "singlestore-host")
spark.conf.set("spark.datasource.singlestore.user", "admin")
spark.conf.set("spark.datasource.singlestore.password", "s3cur3-pa$$word")
The following example configures the singlestore-spark-connector
using the read API:
val df = spark.read
.format("singlestore")
.option("clientEndpoint", "singlestore-host")
.option("user", "admin")
.load("foo")
The following example configures the singlestore-spark-connector
using an external table in Spark SQL:
CREATE TABLE bar USING singlestore OPTIONS ('clientEndpoint'='singlestore-host','dbtable'='foo.bar')
note:
singlestore-spark-connector
doesn't support writing to the reference table for SingleStoreDB Cloud note:singlestore-spark-connector
doesn't support read-only databases for SingleStoreDB Cloud
singlestore-spark-connector
for SingleStoreDB On-Premises
Configure The following example configures the singlestore-spark-connector
globally:
spark.conf.set("spark.datasource.singlestore.ddlEndpoint", "singlestore-master.cluster.internal")
spark.conf.set("spark.datasource.singlestore.dmlEndpoints", "singlestore-master.cluster.internal,singlestore-child-1.cluster.internal:3307")
spark.conf.set("spark.datasource.singlestore.user", "admin")
spark.conf.set("spark.datasource.singlestore.password", "s3cur3-pa$$word")
The following example configures the singlestore-spark-connector
using the read API:
val df = spark.read
.format("singlestore")
.option("ddlEndpoint", "singlestore-master.cluster.internal")
.option("user", "admin")
.load("foo")
The following example configures the singlestore-spark-connector
using an external table in Spark SQL:
CREATE TABLE bar USING singlestore OPTIONS ('ddlEndpoint'='singlestore-master.cluster.internal','dbtable'='foo.bar')
For Java/Python versions of some of these examples, visit the section "Java & Python Example"
Writing to SingleStoreDB
The singlestore-spark-connector
supports saving dataframes to SingleStoreDB using the Spark write API. Here is a basic example of using this API:
df.write
.format("singlestore")
.option("loadDataCompression", "LZ4")
.option("overwriteBehavior", "dropAndCreate")
.mode(SaveMode.Overwrite)
.save("foo.bar") // in format: database.table
If the target table ("foo" in the example above) does not exist in SingleStoreDB the
singlestore-spark-connector
will automatically attempt to create the table. If you
specify SaveMode.Overwrite, if the target table already exists, it will be
recreated or truncated before load. Specify overwriteBehavior = truncate
to truncate rather
than re-create.
Retrieving the number of written rows from taskMetrics
It is possible to add the listener and get the number of written rows.
spark.sparkContext.addSparkListener(new SparkListener() {
override def onTaskEnd(taskEnd: SparkListenerTaskEnd) {
println("Task id: " + taskEnd.taskInfo.id.toString)
println("Records written: " + taskEnd.taskMetrics.outputMetrics.recordsWritten.toString)
}
})
df.write.format("singlestore").save("example")
Specifying keys for tables created by the Spark Connector
When creating a table, the singlestore-spark-connector
will read options prefixed
with tableKey
. These options must be formatted in a specific way in order to
correctly specify the keys.
β οΈ The default table type is a SingleStoreDB columnstore. To create a rowstore table instead, enable thecreateRowstoreTable
option.
To explain we will refer to the following example:
df.write
.format("singlestore")
.option("tableKey.primary", "id")
.option("tableKey.key.created_firstname", "created, firstName")
.option("tableKey.unique", "username")
.mode(SaveMode.Overwrite)
.save("foo.bar") // in format: database.table
In this example, we are creating three keys:
- A primary key on the
id
column - A regular key on the combination of the
firstname
andcreated
columns, with the key namecreated_firstname
- A unique key on the
username
column
Note on (2): Any key can optionally specify a name, just put it after the key type. Key names must be unique.
To change the default ColumnStore sort key you can specify it explicitly:
df.write
.option("tableKey.columnstore", "id")
You can also customize the shard key like so:
df.write
.option("tableKey.shard", "id, timestamp")
Inserting rows into the table with ON DUPLICATE KEY UPDATE
When updating a table it is possible to insert rows with ON DUPLICATE KEY UPDATE
option.
See sql reference for more details.
β οΈ This feature doesn't work for columnstore tables with SingleStoreDB 7.1.
df.write
.option("onDuplicateKeySQL", "age = age + 1")
.option("insertBatchSize", 300)
.mode(SaveMode.Append)
.save("foo.bar")
As a result of the following query, all new rows will be appended without changes.
If a row with the same PRIMARY KEY
or UNIQUE
index already exists then the corresponding age
value will be increased.
When you use ON DUPLICATE KEY UPDATE, all rows of the DataFrame are split into batches, and every insert query will contain no more than the specified insertBatchSize
rows setting.
Save Modes
Save operations can optionally take a SaveMode, that specifies how to handle existing data if present. It is important to realize that these save modes do not utilize any locking and are not atomic.
SaveMode.Append
means that when saving a DataFrame to a data source, if data/table already exists, contents of the DataFrame are expected to be appended to existing data.SaveMode.Overwrite
means that when saving a DataFrame to a data source, if data/table already exists, existing data is expected to be overwritten by the contents of the DataFrame.
Overwrite
mode depends onoverwriteBehavior
option, for better understanding look at the section "Merging on save"
SaveMode.ErrorIfExists
means that when saving a DataFrame to a data source, if data already exists, an exception is expected to be thrown.SaveMode.Ignore
means that when saving a DataFrame to a data source, if data already exists, contents of the DataFrame are expected to be appended to existing data and all rows with duplicate key are ignored.
SaveMode
option
Example of df.write
.mode(SaveMode.Append)
.save("foo.bar")
Merging on save
When saving dataframes or datasets to SingleStoreDB, you can manage how SaveMode.Overwrite is interpreted by the connector via the option overwriteBehavior. This option can take one of the following values:
dropAndCreate
(default) - drop and create the table before writing new values.truncate
- truncate the table before writing new values.merge
- replace rows with new rows by matching on the primary key. (Use this option only if you need to fully rewrite existing rows with new ones. To specify some rule for the update, use theonDuplicateKeySQL
option instead.)
All these options are case-insensitive.
merge
option
Example of Suppose you have the following table, and the Id
column is the primary key.
SELECT * FROM <table>;
Id | Name | Age |
---|---|---|
1 | Alice | 20 |
2 | Bob | 25 |
3 | Charlie | 30 |
If you save the following dataframe with overwriteBehavior = merge
:
Id | Name | Age |
---|---|---|
2 | Daniel | 22 |
3 | Eve | 27 |
4 | Franklin | 35 |
df.write
.format("singlestore")
.option("overwriteBehavior", "merge")
.mode(SaveMode.Overwrite)
.save("<yourdb>.<table>")
After the save is complete, the table will look like this:
note: rows with Id=2 and Id=3 were overwritten with new rows
note: the row with Id=1 was not touched and still exists in the result
SELECT * FROM <table>;
Id | Name | Age |
---|---|---|
1 | Alice | 20 |
2 | Daniel | 22 |
3 | Eve | 27 |
4 | Franklin | 35 |
SQL Pushdown
The singlestore-spark-connector
has extensive support for rewriting Spark SQL
and dataframe operation query plans into standalone SingleStoreDB queries.
This allows most of the computation to be pushed into the SingleStoreDB distributed system
without any manual intervention. The SQL rewrites are enabled automatically,
but they can be disabled using the disablePushdown
option.
The singlestore-spark-connector
also support partial pushdown,
where certain parts of a query can be evaluated in SingleStoreDB
and certain parts can be evaluated in Spark.
β οΈ SQL Pushdown is either enabled or disabled on the entire Spark Session. If you want to run multiple queries in parallel with different values ofdisablePushdown
, make sure to run them on separate Spark Sessions.
We currently support most of the primary Logical Plan nodes in Spark SQL including:
- Project
- Filter
- Aggregate
- Window
- Join
- Limit
- Sort
We also support most Spark SQL expressions. A full list of supported operators/functions can be found in the ExpressionGen.scala file.
The best place to look for examples of fully supported queries is in the tests. Check out this file as a starting point: SQLPushdownTest.scala.
Debugging SQL Pushdown
If you encounter an issue with SQL Pushdown the first step is to look at the
explain. You can do this easily from any dataframe using the function
df.explain()
. If you pass the argument true
you will get a lot more output
that includes pre and post optimization passes.
In addition, the singlestore-spark-connector
outputs a lot of helpful information
when the TRACE log level is enabled for the com.singlestore.spark
package.
To enable TRACE log level, add the following line(s) to the log4j configuration:
- Log4j
log4j.logger.com.singlestore.spark=TRACE
- Log4j 2
logger.singlestore.name = com.singlestore.spark
logger.singlestore.level = TRACE
logger.singlestore.additivity = false
Make sure not to leave it in place since it generates a huge amount of tracing output.
SQL Pushdown Incompatibilities
ToUnixTimestamp
andUnixTimestamp
only handle time values less than2038-01-19 03:14:08
, if they getDateType
orTimestampType
as a first argument.FromUnixTime
withyyyy-MM-dd HH:mm:ss
as the default format, only handles time less than2147483648
(2^31
).DecimalType
is truncated on overflow (by default, Spark either throws an exception or returns null).greatest
andleast
returnnull
if at least one argument isnull
(in Spark these functions skip nulls).- When a value can not be converted to numeric or fractional type SingleStoreDB returns 0 (Spark returns
null
). Atanh(x)
, for x β (-β, -1] βͺ [1, β) returns,null
(Spark returnsNaN
).- When a string is cast to a numeric type, SingleStoreDB takes the prefix of it which is numeric (Spark returns
null
if the whole string is not numeric). - When a numeric type is cast to a smaller one (in size), SingleStoreDB truncates it. For example
500
cast to theByte
will be127
. Note: Spark optimizer can optimize casts for literals and then the behaviour for literals matches custom Spark behaviour. - When a fractional type is cast to an integral type, SingleStoreDB rounds it to the closest value.
Log
returnsnull
instead ofNaN
,Infinity
,-Infinity
.Round
rounds down if the number to be rounded is followed by 5, and it isDOUBLE
orFLOAT
(DECIMAL
is rounded up).Conv
works differently if the number contains non-alphanumeric characters.ShiftLeft
,ShiftRight
, andShiftRightUnsigned
convert the value to anUNSIGNED BIGINT
and then produce the shift. In case of an overflow, it returns0
(1<<64
=0
and10>>20
=0
).BitwiseGet
returns 0 when the bit position is negative or exceeds the bit upper limit.Initcap
defines a letter as the beginning of a word even if it is enclosed in quotation marks, brackets, etc. For example "dear sir/madam (miss)" is converted to "Dear Sir/Madam (Miss)".Skewness(x)
, in Spark 3.0, forSTD(x) = 0
returnsnull
instead ofNaN
.
Parallel Read Support
Parallel read can be enabled using enableParallelRead
option. This can drastically improve performance in some cases.
The enableParallelRead
option can have one of the following values:
disabled
: Disables parallel reads and performs non-parallel reads.automaticLite
: Performs parallel reads if at least one parallel read feature specified inparallelRead.Features
is supported. Otherwise performs a non-parallel read. InautomaticLite
mode, after push down of the outer sorting operation (for example, a nestedSELECT
statement where sorting is done in a top-levelSELECT
) into SingleStoreDB is done, a non-parallel read is used.automatic
: Performs parallel reads if at least one parallel read feature specified inparallelRead.Features
is supported. Otherwise performs a non-parallel read. Inautomatic
mode, thesinglestore-spark-connector
is unable to push down an outer sorting operation into SingleStore. Final sorting is done at the Spark end of the operation.forced
: Performs parallel reads if at least one parallel read feature specified inparallelRead.Features
is supported. Otherwise it returns an error. Inforced
mode, thesinglestore-spark-connector
is unable to push down an outer sorting operation into SingleStore. Final sorting is done at the Spark end of the operation.
By default, enableParallelRead
is set to automaticLite
.
Parallel read features
The SingleStoreDB Spark Connector supports the following parallel read features:
readFromAggregators
readFromAggregatorsMaterialized
readFromLeaves
The connector uses the first feature specified in parallelRead.Features
which meets all the requirements.
The requirements for each feature are specified below.
By default, the connector uses the readFromAggregators
feature.
You can repartition the result set for readFromAggregators
and readFromAggregatorsMaterialized
features.
See Parallel Read Repartitioning for more information.
readFromAggregators
When this feature is used, the singlestore-spark-connector
will use SingleStoreDB parallel read functionality.
By default, the number of partitions in the resulting DataFrame is the least of the number of partitions in the SingleStoreDB database and Spark parallelism level
(i.e., sum of (spark.executor.cores/spark.task.cpus)
for all executors).
Number of partitions in the resulting DataFrame can be controlled using parallelRead.maxNumPartitions
option.
To use this feature, all reading tasks must start at the same time. Hence, the number of partitions in the resulting DataFrame should not be greater than the parallelism level of the Spark cluster.
Use the parallelRead.tableCreationTimeoutMS
option to specify a timeout for result table creation.
Requirements:
- SingleStoreDB version 7.5+
- Either the
database
option is set, or the database name is specified in theload
option - SingleStoreDB parallel read functionality supports the generated query
readFromAggregatorsMaterialized
This feature is very similar to readFromAggregators
. The only difference is that readFromAggregatorsMaterialized
uses the
MATERIALIZED
option to create the result table. When this feature is used, the reading tasks do not have to start at the same time.
Hence, the parallelism level on the Spark cluster does not affect the reading tasks.
Although, using the MATERIALIZED
option may cause a query to fail if SingleStoreDB does not have enough memory to materialize the result set.
By default, the number of partitions in the resulting DataFrame is equal to the number of partitions in the SingleStoreDB database.
Number of partitions in the resulting DataFrame can be controlled using parallelRead.maxNumPartitions
option.
Use the parallelRead.tableCreationTimeoutMaterializedMS
option to specify a timeout for materialized result table creation.
Requirements:
- SingleStoreDB version 7.5+
- Either the
database
option is set, or the database name is specified in theload
option - SingleStoreDB parallel read functionality supports the generated query
readFromLeaves
When this feature is used, the singlestore-spark-connector
skips the transaction layer and reads directly from partitions on the leaf nodes.
Hence, each individual read task sees an independent version of the database's distributed state.
If some queries (other than read operation) are run on the database, they may affect the current read operation.
Make sure to take this into account when using readFromLeaves
feature.
This feature supports only those query-shapes that do not perform any operation on the aggregator and can be pushed down to the leaf nodes.
In order to use readFromLeaves
feature, the username and password provided to the
singlestore-spark-connector
must be the same across all nodes in the cluster.
By default, the number of partitions in the resulting DataFrame is equal to the number of partitions in the SingleStoreDB database.
Number of partitions in the resulting DataFrame can be controlled using parallelRead.maxNumPartitions
option.
Requirements:
- Either the
database
option is set, or the database name is specified in theload
option - The username and password provided to the
singlestore-spark-connector
must be uniform across all the nodes in the cluster, because parallel reads require consistent authentication and connectible leaf nodes - The hostnames and ports listed by
SHOW LEAVES
must be directly connectible from Spark - The generated query can be pushed down to the leaf nodes
Parallel read repartitioning
You can repartition the result using parallelRead.repartition
option for the readFromAggregators
and readFromAggregatorsMaterialized
features
to ensure that each task reads approximately the same amount of data.
This option is very useful for queries with top level limit clauses as without repartitioning it is possible that all rows will belong to one partition.
Use the parallelRead.repartition.columns
option to specify a comma separated list of columns that will be used for repartitioning.
Column names that contain leading or trailing whitespaces or commas must be escaped as:
- Column name must be enclosed in backticks
"a" -> "`a`"
- Each backtick (`) in the column name must be replaced with two backticks (``)
"a`a``" -> "a``a````"
By default, repartitioning is done using an additional column with RAND()
value.
Example
spark.read.format("singlestore")
.option("enableParallelRead", "automatic")
.option("parallelRead.Features", "readFromAggregators,readFromLeaves")
.option("parallelRead.repartition", "true")
.option("parallelRead.repartition.columns", "a, b")
.option("parallelRead.TableCreationTimeout", "1000")
.load("db.table")
In the following example, connector will check requirements for readFromAggregators
.
If they are satisfied, it will use this feature.
Otherwise, it will check requirements for readFromLeaves
.
If they are satisfied, connector will use this feature. Otherwise, it will use non-parallel read.
If the connector uses readFromAggregators
, it will repartition the result on the SingleStoreDB side before reading it,
and it will fail if creation of the result table will take longer than 1000
milliseconds.
Running SQL queries
The methods executeSinglestoreQuery(query: String, variables: Any*)
and executeSinglestoreQueryDB(db: String, query: String, variables: Any*)
allow you to run SQL queries on a SingleStoreDB database directly using the existing SparkSession
object. The method executeSinglestoreQuery
uses the database defined in the SparkContext
object you use. executeSinglestoreQueryDB
allows you to specify the database that
will be used for querying.
The following examples demonstrate their usage (assuming you already have
initialized SparkSession
object named spark
). The methods return Iterator[org.apache.spark.sql.Row]
object.
// this imports the implicit class QueryMethods which adds the methods
// executeSinglestoreQuery and executeSinglestoreQueryDB to SparkSession class
import com.singlestore.spark.SQLHelper.QueryMethods
// You can pass an empty database to executeSinglestoreQueryDB to connect to SingleStoreDB without specifying a database.
// This allows you to create a database which is defined in the SparkSession config for example.
spark.executeSinglestoreQueryDB("", "CREATE DATABASE foo")
// the next query can be used if the database field has been specified in spark object
s = spark.executeSinglestoreQuery("CREATE TABLE user(id INT, name VARCHAR(30), status BOOLEAN)")
// you can create another database
spark.executeSinglestoreQuery("CREATE DATABASE bar")
// the database specified as the first argument will override the database set in the SparkSession object
s = spark.executeSinglestoreQueryDB("bar", "CREATE TABLE user(id INT, name VARCHAR(30), status BOOLEAN)")
You can pass query parameters to the functions as arguments following query
. The supported types for parameters are String, Int, Long, Short, Float, Double, Boolean, Byte, java.sql.Date, java.sql.Timestamp
.
import com.singlestore.spark.SQLHelper.QueryMethods
var userRows = spark.executeSinglestoreQuery("SELECT id, name FROM USER WHERE id > ? AND status = ? AND name LIKE ?", 10, true, "%at%")
for (row <- userRows) {
println(row.getInt(0), row.getString(1))
}
Alternatively, these functions can take SparkSession
object as the first argument, as in the example below
import com.singlestore.spark.SQLHelper.{executeSinglestoreQuery, executeSinglestoreQueryDB}
executeSinglestoreQuery(spark, "CREATE DATABASE foo")
var s = executeSinglestoreQueryDB(spark, "foo", "SHOW TABLES")
Security
SQL Permissions
The permission matrix describes the permissions required to run each command.
To perform any SQL operation through the SingleStore Spark Connector, you must have the permissions required for that specific operation. The following matrix describes the minimum permissions required to perform some operations.
Note: The ALL PRIVILEGES permission allows you to perform any operation.
Operation | Min. Permission | Alternative Permission |
---|---|---|
READ from collection |
SELECT |
ALL PRIVILEGES |
WRITE to collection |
SELECT, INSERT |
ALL PRIVILEGES |
DROP database or collection |
SELECT, INSERT, DROP |
ALL PRIVILEGES |
CREATE database or collection |
SELECT, INSERT, CREATE |
ALL PRIVILEGES |
For more information on granting privileges, see GRANT
Connecting with a Kerberos-authenticated User
You can use the SingleStoreDB Spark Connector with a Kerberized user without any additional configuration.
To use a Kerberized user, you need to configure the connector with the given SingleStoreDB database user that is authenticated with Kerberos
(via the user
option). Please visit our documentation here
to learn about how to configure SingleStoreDB users with Kerberos.
Here is an example of configuring the Spark connector globally with a Kerberized SingleStoreDB user called krb_user
.
spark = SparkSession.builder()
.config("spark.datasource.singlestore.user", "krb_user")
.getOrCreate()
You do not need to provide a password when configuring a Spark Connector user that is Kerberized. The connector driver (SingleStoreDB JDBC driver) will be able to authenticate the Kerberos user from the cache by the provided username. Other than omitting a password with this configuration, using a Kerberized user with the Connector is no different than using a standard user. Note that if you do provide a password, it will be ignored.
SSL Support
The SingleStoreDB Spark Connector uses the SingleStoreDB JDBC Driver under the hood and thus supports SSL configuration out of the box. In order to configure SSL, first ensure that your SingleStoreDB cluster has SSL configured. Documentation on how to set this up can be found here: https://docs.singlestore.com/latest/guides/security/encryption/ssl/
Once you have setup SSL on your server, you can enable SSL via setting the following options:
spark.conf.set("spark.datasource.singlestore.useSSL", "true")
spark.conf.set("spark.datasource.singlestore.serverSslCert", "PATH/TO/CERT")
Note: the serverSslCert
option may be server's certificate in DER form, or the server's
CA certificate. Can be used in one of 3 forms:
serverSslCert=/path/to/cert.pem
(full path to certificate)serverSslCert=classpath:relative/cert.pem
(relative to current classpath)- or as verbatim DER-encoded certificate string
------BEGIN CERTIFICATE-----...
You may also want to set these additional options depending on your SSL configuration:
spark.conf.set("spark.datasource.singlestore.trustServerCertificate", "true")
spark.conf.set("spark.datasource.singlestore.disableSslHostnameVerification", "true")
See The SingleStoreDB JDBC Driver for more information.
JWT authentication
You may authenticate your connection to the SingleStoreDB cluster using the SingleStoreDB Spark connector with a JWT. To use JWT-based authentication, specify the following parameters:
credentialType=JWT
password=<jwt-token>
Here's a sample configuration that uses JWT-based authentication:
SparkConf conf = new SparkConf();
conf.set("spark.datasource.singlestore.ddlEndpoint", "singlestore-master.cluster.internal")
conf.set("spark.datasource.singlestore.dmlEndpoints", "singlestore-master.cluster.internal,singlestore-child-1.cluster.internal:3307")
conf.set("spark.datasource.singlestore.credentialType", "JWT")
conf.set("spark.datasource.singlestore.useSsl", "true")
conf.set("spark.datasource.singlestore.user", "s2user")
conf.set("spark.datasource.singlestore.password", "eyJhbGci.eyJzdWIiOiIxMjM0NTY3.masHf")
note: To authenticate your connection to the SingleStoreDB cluster using the SingleStoreDB Spark connector with a JWT, the SingleStoreDB user must connect via SSL and use a JWT for authentication.
See Create a JWT User for more information.
See Authenticate via JWT for more information.
Filing issues
When filing issues please include as much information as possible as well as any reproduction steps. It's hard for us to reproduce issues if the problem depends on specific data in your SingleStoreDB table for example. Whenever possible please try to construct a minimal reproduction of the problem and include the table definition and table contents in the issue.
If the issue is related to SQL Pushdown (or you aren't sure) make sure to include the TRACE output (from the com.singlestore.spark package) or the full explain of the plan. See the debugging SQL Pushdown section above for more information on how to do this.
Happy querying!
Setting up development environment
- install Oracle JDK 8 from this url: https://www.oracle.com/java/technologies/javase/javase-jdk8-downloads.html
- install the community edition of Intellij IDEA from https://www.jetbrains.com/idea/
- clone the repository https://github.com/memsql/singlestore-spark-connector.git
- in Intellij IDEA choose
Configure->Plugins
and install Scala plugin - in Intellij IDEA run
Import Project
and select path to singlestore-spark-connectorbuild.sbt
file - choose
import project from external model
andsbt
- in
Project JDK
selectNew...->JDK
and choose the path to the installed JDK Finish
- it will overwrite some files and create build files (which are in .gitignore)
- you may need to remove the
.idea
directory for IDEA to load the project properly - in Intellij IDEA choose
File->Close Project
- run
git checkout .
to revert all changes made by Intellij IDEA - in Intellij IDEA choose
Open
and select path to singlestore-spark-connector - run
Test Spark 3.0
(it should succeed)
Java & Python Examples
Java
Configuration
SparkConf conf = new SparkConf();
conf.set("spark.datasource.singlestore.ddlEndpoint", "singlestore-master.cluster.internal")
conf.set("spark.datasource.singlestore.dmlEndpoints", "singlestore-master.cluster.internal,singlestore-child-1.cluster.internal:3307")
conf.set("spark.datasource.singlestore.user", "admin")
conf.set("spark.datasource.singlestore.password", "s3cur3-pa$$word")
Read Data
DataFrame df = spark
.read()
.format("singlestore")
.option("ddlEndpoint", "singlestore-master.cluster.internal")
.option("user", "admin")
.load("foo");
Write Data
df.write()
.format("singlestore")
.option("loadDataCompression", "LZ4")
.option("overwriteBehavior", "dropAndCreate")
.mode(SaveMode.Overwrite)
.save("foo.bar")
Python
Configuration
spark.conf.set("spark.datasource.singlestore.ddlEndpoint", "singlestore-master.cluster.internal")
spark.conf.set("spark.datasource.singlestore.dmlEndpoints", "singlestore-master.cluster.internal,singlestore-child-1.cluster.internal:3307")
spark.conf.set("spark.datasource.singlestore.user", "admin")
spark.conf.set("spark.datasource.singlestore.password", "s3cur3-pa$$word")
Read Data
df = spark \
.read \
.format("singlestore") \
.option("ddlEndpoint", "singlestore-master.cluster.internal") \
.option("user", "admin") \
.load("foo")
Write Data
df.write \
.format("singlestore") \
.option("loadDataCompression", "LZ4") \
.option("overwriteBehavior", "dropAndCreate") \
.mode("overwrite") \
.save("foo.bar")