Run Apache Hive queries using PowerShell

Artikkeli
09/06/2024

This document provides an example of using Azure PowerShell to run Apache Hive queries in an Apache Hadoop on HDInsight cluster.

Note

This document does not provide a detailed description of what the HiveQL statements that are used in the examples do. For information on the HiveQL that is used in this example, see Use Apache Hive with Apache Hadoop on HDInsight.

Prerequisites

An Apache Hadoop cluster on HDInsight. See Get Started with HDInsight on Linux.
The PowerShell Az Module installed.

Run a Hive query

Azure PowerShell provides cmdlets that allow you to remotely run Hive queries on HDInsight. Internally, the cmdlets make REST calls to WebHCat on the HDInsight cluster.

The following cmdlets are used when running Hive queries in a remote HDInsight cluster:

Connect-AzAccount: Authenticates Azure PowerShell to your Azure subscription.
New-AzHDInsightHiveJobDefinition: Creates a job definition by using the specified HiveQL statements.
Start-AzHDInsightJob: Sends the job definition to HDInsight and starts the job. A job object is returned.
Wait-AzHDInsightJob: Uses the job object to check the status of the job. It waits until the job completes or the wait time is exceeded.
Get-AzHDInsightJobOutput: Used to retrieve the output of the job.
Invoke-AzHDInsightHiveJob: Used to run HiveQL statements. This cmdlet blocks the query completes, then returns the results.
Use-AzHDInsightCluster: Sets the current cluster to use for the Invoke-AzHDInsightHiveJob command.

The following steps demonstrate how to use these cmdlets to run a job in your HDInsight cluster:

Using an editor, save the following code as hivejob.ps1.

# Login to your Azure subscription
$context = Get-AzContext
if ($context -eq $null) 
{
    Connect-AzAccount
}
$context

#Get cluster info
$clusterName = Read-Host -Prompt "Enter the HDInsight cluster name"
$creds=Get-Credential -Message "Enter the login for the cluster"

#HiveQL
#Note: set hive.execution.engine=tez; is not required for
#      Linux-based HDInsight
$queryString = "set hive.execution.engine=tez;" +
            "DROP TABLE log4jLogs;" +
            "CREATE EXTERNAL TABLE log4jLogs(t1 string, t2 string, t3 string, t4 string, t5 string, t6 string, t7 string) ROW FORMAT DELIMITED FIELDS TERMINATED BY ' ' STORED AS TEXTFILE LOCATION 'wasbs:///example/data/';" +
            "SELECT * FROM log4jLogs WHERE t4 = '[ERROR]';"

#Create an HDInsight Hive job definition
$hiveJobDefinition = New-AzHDInsightHiveJobDefinition -Query $queryString 

#Submit the job to the cluster
Write-Host "Start the Hive job..." -ForegroundColor Green

$hiveJob = Start-AzHDInsightJob -ClusterName $clusterName -JobDefinition $hiveJobDefinition -ClusterCredential $creds

#Wait for the Hive job to complete
Write-Host "Wait for the job to complete..." -ForegroundColor Green
Wait-AzHDInsightJob -ClusterName $clusterName -JobId $hiveJob.JobId -ClusterCredential $creds

# Print the output
Write-Host "Display the standard output..." -ForegroundColor Green
Get-AzHDInsightJobOutput `
    -Clustername $clusterName `
    -JobId $hiveJob.JobId `
    -HttpCredential $creds

Open a new Azure PowerShell command prompt. Change directories to the location of the hivejob.ps1 file, then use the following command to run the script:
```
.\hivejob.ps1
```
When the script runs, you're prompted to enter the cluster name and the HTTPS/Cluster Admin account credentials. You may also be prompted to sign in to your Azure subscription.

When the job completes, it returns information similar to the following text:

Display the standard output...
2012-02-03      18:35:34        SampleClass0    [ERROR] incorrect       id
2012-02-03      18:55:54        SampleClass1    [ERROR] incorrect       id
2012-02-03      19:25:27        SampleClass4    [ERROR] incorrect       id

As mentioned earlier, Invoke-Hive can be used to run a query and wait for the response. Use the following script to see how Invoke-Hive works:

# Login to your Azure subscription
$context = Get-AzContext
if ($context -eq $null) 
{
    Connect-AzAccount
}
$context

#Get cluster info
$clusterName = Read-Host -Prompt "Enter the HDInsight cluster name"
$creds=Get-Credential -Message "Enter the login for the cluster"

# Set the cluster to use
Use-AzHDInsightCluster -ClusterName $clusterName -HttpCredential $creds

$queryString = "set hive.execution.engine=tez;" +
            "DROP TABLE log4jLogs;" +
            "CREATE EXTERNAL TABLE log4jLogs(t1 string, t2 string, t3 string, t4 string, t5 string, t6 string, t7 string) ROW FORMAT DELIMITED FIELDS TERMINATED BY ' ' STORED AS TEXTFILE LOCATION '/example/data/';" +
            "SELECT * FROM log4jLogs WHERE t4 = '[ERROR]';"
Invoke-AzHDInsightHiveJob `
    -StatusFolder "statusout" `
    -Query $queryString

The output looks like the following text:

2012-02-03    18:35:34    SampleClass0    [ERROR]    incorrect    id
2012-02-03    18:55:54    SampleClass1    [ERROR]    incorrect    id
2012-02-03    19:25:27    SampleClass4    [ERROR]    incorrect    id

Note

For longer HiveQL queries, you can use the Azure PowerShell Here-Strings cmdlet or HiveQL script files. The following snippet shows how to use the Invoke-Hive cmdlet to run a HiveQL script file. The HiveQL script file must be uploaded to wasbs://.

Invoke-AzHDInsightHiveJob -File "wasbs://<ContainerName>@<StorageAccountName>/<Path>/query.hql"

For more information about Here-Strings, see HERE-STRINGS.

Troubleshooting

If no information is returned when the job completes, view the error logs. To view error information for this job, add the following to the end of the hivejob.ps1 file, save it, and then run it again.

# Print the output of the Hive job.
Get-AzHDInsightJobOutput `
        -Clustername $clusterName `
        -JobId $job.JobId `
        -HttpCredential $creds `
        -DisplayOutputType StandardError

This cmdlet returns the information that is written to STDERR during job processing.

Summary

As you can see, Azure PowerShell provides an easy way to run Hive queries in an HDInsight cluster, monitor the job status, and retrieve the output.

Next steps

For general information about Hive in HDInsight:

Use Apache Hive with Apache Hadoop on HDInsight

For information about other ways you can work with Hadoop on HDInsight:

Use MapReduce with Apache Hadoop on HDInsight

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