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AMPS Server Documentation 5.3.4
AMPS Server Documentation 5.3.4
  • Welcome to AMPS 5.3.4
  • Introduction to AMPS
    • Overview of AMPS
    • Getting Started With AMPS
      • Installing AMPS
      • Starting AMPS
      • JSON Messages - A Quick Primer
      • spark: the AMPS command-line client
      • Evaluating AMPS on Windows or MacOS
      • Galvanometer and RESTful Statistics
    • AMPS Basics: Subscribe and Publish to Topics
    • State of the World (SOW): The Message Database
      • When Should I Store a Topic in the SOW?
      • How Does the SOW Work?
      • Configuration
      • Queries
      • Atomic Query and Subscribe
      • Advanced Messaging and the SOW
    • Record and Replay Messages with the AMPS Transaction Log
    • Message Queues
    • Scenario and Feature Reference
      • Recovery Strategies
    • Getting Support
    • Advanced Topics
    • Next Steps
  • AMPS Evaluation Guide
    • Introduction
    • Evaluation and Development with AMPS
    • Tips on Measuring Performance
    • Next Steps
  • AMPS User Guide
    • Introduction
      • Product Overview
      • Requirements
      • Organization of this Guide
        • Documentation Conventions
      • Technical Support
    • Installing and Starting AMPS
      • Installing AMPS
      • Starting AMPS
      • Production Configuration
    • Subscribe and Publish
      • Topics
      • Filtering Subscriptions by Content
      • Conflated Subscriptions
      • Replacing Subscriptions
      • Messages in AMPS
      • Message Ordering
      • Retrieving Part of a Message
    • AMPS Expressions
      • Syntax
      • Identifiers
      • AMPS Data Types
      • Grouping and Order of Evaluation
      • Logical Operators
      • Arithmetic Operators
      • Comparison Operators
      • LIKE Operator
      • Conditional Operators
      • Working with Arrays
      • Regular Expressions
      • Performance Considerations
    • AMPS Functions
      • AMPS Function Overview
      • String Comparison Functions
      • Concatenating Strings
      • Managing String Case
      • Replacing Text in Strings
      • String Manipulation Functions
      • Date and Time Functions
      • Array Reduce Functions
      • Geospatial Functions
      • Numeric Functions
      • CRC Functions
      • Message Functions
      • Client Functions
      • Coalesce Function
      • AMPS Information Functions
      • Typed Value Creation
      • Constructing Fields
      • Aggregate Functions
    • State of the World (SOW) Topics
      • How Does the SOW Work?
      • Using the State of the World
      • Understanding SOW Keys
      • Indexing SOW Topics
      • Programmatically Deleting Records from the Topic State
      • SOW Maintenance
        • Creating a Maintenance Schedule for a Topic
        • Setting Per-Message Lifetime
      • Storing Multiple Logical Topics in One Physical Topic
    • Querying the State of the World (SOW)
      • Overview of SOW Queries
      • Query and Subscribe
      • Historical SOW Topic Queries
      • Managing Result Sets
      • Batching Query Results
    • Out-of-Focus Messages (OOF)
    • State of the World Message Enrichment
    • Incremental Message Updates
      • Using Delta Publish
      • Understanding Delta Publish
      • Delta Publish Support
    • Receiving Only Updated Fields
      • Using Delta Subscribe
      • Identifying Changed Records
      • Conflated Subscriptions and Delta Subscribe
      • Select List and Delta Subscribe
      • Options for Delta Subscribe
    • Conflated Topics
    • Aggregation and Analytics
      • Understanding Views
      • Defining Views and Aggregations
      • Constructing Field Contents
      • Best Practices for Views
      • View Examples
      • Aggregated Subscriptions
    • Record and Replay Messages
      • Using the Transaction Log and Bookmark Subscriptions
      • Understanding Message Persistence
      • Configuring a Transaction Log
      • Replaying Messages with Bookmark Subscription
      • Managing Journal Files
      • Using amps-grep to Search the Journal
    • Message Queues
      • Getting Started with AMPS Queues
      • Understanding AMPS Queuing
      • Advanced Messaging and Queues
      • Replacing Queue Subscriptions
      • Handling Unprocessed Messages
      • Advanced Queue Configuration
      • Queue Subscriptions Compared to Bookmark Replays
    • Message Types
      • Default Message Types
      • BFlat Messages
      • MessagePack Messages
      • Composite Messages
      • Protobuf Message Types
      • Struct Message Types
    • Command Acknowledgment
      • Requesting Acknowledgments
      • Receiving Acknowledgments
      • Bookmark Subscriptions and Completed Acknowledgments
      • Bookmark Subscriptions and Persisted Acknowledgments
      • Acknowledgment Conflation and Publish Acknowledgements
    • Transports
      • Client Connections
      • Replication Connections
      • Transport Filters
    • Running AMPS as a Linux Service
      • Installing the Service
      • Configuring the Service
      • Managing the Service
      • Uninstalling the Service
    • Logging
      • Configuring Logging
      • Log Message Format
      • Message Levels
      • Message Categories
      • Logging to a File
      • Logging to a Compressed File
      • Logging to Syslog
      • Logging to the Console
      • Looking up Errors with ampserr
    • Event Topics
      • Client Status Events
      • SOW Statistics Events
      • Persisting Event Topics
    • Utilities
      • Command-Line Basic Client
      • Dump clients.ack File
      • Dump journal File
      • Dump queues.ack File
      • Dump SOW File
      • Dump Journal Topic Index File
      • Find Bookmark or Transaction ID in Transaction Log
      • Find Information in Error Log or Transaction Log
      • Identify Type of AMPS File
      • List/Explain Error Codes
      • Query Statistics Database
      • Statistics Database Report
      • Storage Performance Testing
      • Submit Minidump to 60East
      • Obsolete Utility: Upgrade File Formats
    • Monitoring AMPS
      • Statistics Collection
        • Time Range Selection
        • Output Formatting
      • Galvanometer
      • Configuring Monitoring
    • Automating AMPS with Actions
    • Replicating Messages Between Instances
      • Replication Basics
      • Configuring Replication
      • Replication Configuration Validation
      • Replication Resynchronization
      • Replication Compression
      • Destination Server Failover
      • Two-Way Replication
      • PassThrough Replication
      • Guarantees on Ordering
      • Replication Security
      • Understanding Replication Message Routing
      • Replicated Queues
      • Replication Best Practices
    • Highly Available AMPS Installations
      • Overview of High Availability
        • Example: Pair of Instances for Failover
        • Example: Regional Distribution
        • Example: Regional Distribution with HA
        • Example: Hub and Spoke / Expandable Mesh
      • Details of High Availability
      • Slow Client Management and Capacity Limits
      • Message Ordering Considerations
    • Operation and Deployment
      • Capacity Planning
      • Linux OS Settings
      • Upgrading AMPS
      • Using AMPS with a Proxy
      • Operations Best Practices
    • Securing AMPS
      • Authentication
      • Entitlement
      • Providing an Identity for Outbound Connections
      • Protecting Data in Transit Using TLS/SSL
    • Troubleshooting AMPS
      • Planning for Troubleshooting
      • Diagnostic Utilities
      • Finding Information in the Log
      • Reading Replication Log Messages
      • Troubleshooting Disconnected Clients
      • Troubleshooting Regular Expression Subscriptions
    • AMPS Distribution Layout
    • Optionally-Loaded Modules
      • Optional Functions
        • Legacy Messaging Functions
        • Special-Purpose Functions
      • Optional SOW Key Generator
        • Chaining Key Generator
      • Optional Authentication/Entitlements Modules
        • RESTful Authentication and Entitlements
        • Multimethod Authentication Module
        • Simple Access Entitlements Module
      • Optional Authenticator Modules
        • Multimethod Authenticator
        • Command Execution Authenticator
    • AMPS Statistics
    • File Format Versions
  • AMPS Configuration Guide
    • AMPS Configuration Basics
      • Getting Started With AMPS Configuration
      • Units, Intervals, and Environment Variables
      • Working With Configuration Files
      • Including External Files
    • Instance Level Configuration
    • Admin Server and Statistics
    • Modules
    • Message Types
    • Transports
    • Logging
    • State of the World (SOW)
      • SOW/Topic
      • SOW/*Queue
      • SOW/ConflatedTopic
      • SOW/View
    • Replication
      • Replication Validation
    • Transaction Log
    • Authentication
    • Entitlement
    • Actions
      • Configuration for Actions
      • Choosing When an Action Runs
        • On a Schedule
        • On AMPS Startup or Shutdown
        • On a Linux Signal
        • On a REST Request
        • On Minidump Creation
        • On Client Connect or Disconnect
        • On Client Logon
        • On Client Offline Message Buffering
        • On Subscribe or Unsubscribe
        • On Incoming Replication Connections
        • On Outgoing Replication Connections
        • On Message Published to AMPS
        • On Message Delivered to Subscriber
        • On Message Affinity
        • On SOW Message Expiration
        • On SOW Message Delete
        • On OOF Message
        • On Message Condition Timeout
        • On Message State Change
        • On a Custom Event
      • Choosing What an Action Does
        • Rotate Error/Event Log
        • Compress Files
        • Truncate Statistics
        • Manage Transaction Log Journal Files
        • Remove Files
        • Delete SOW Messages
        • Compact SOW Topic
        • Query SOW Topic
        • Manage Security
        • Enable or Disable Transports
        • Publish Message
        • Manage Replication Acknowledgment
        • Extract Values from a Message
        • Translate Data Within an Action
        • Increment Counter
        • Raise a Custom Event
        • Execute System Command
        • Manage Queue Transfers
        • Create Minidump
        • Shut Down AMPS
        • Debug Action Configuration
      • Conditionally Stopping an Action
        • Based on File System Capacity
        • Based on an Expression
      • Examples of Action Configuration
        • Archive Journals Once a Week
        • Archive Journals On RESTful Command
        • Record Expired Queue Messages to a Dead Letter Topic
        • Copy Messages that Exceed a Timeout to a Different Topic
        • Deactivate and Reactivate Security on Signals
        • Reset Entitlements for a Disconnected Client
        • Extract Values from a Published Message
        • Shut Down AMPS When a Filesystem Is Full
        • Increment a Counter and Echo a Message
    • Protocols
  • AMPS Monitoring Guide
    • Statistics Types
    • Table Reference
    • Administrative Actions
    • Host Statistics
      • cpu
      • disks
      • memory
      • name
      • network
    • AMPS Instance Statistics
      • api
      • clients
      • config.xml
      • config_path
      • conflated_topics
      • cpu
      • cwd
      • description
      • environment
      • lifetimes
      • logging
      • memory
      • message_types
      • name
      • name_hash
      • pid
      • processors
      • queues
      • queries
      • replication
      • sow
      • statistics
      • subscriptions
      • timestamp
      • transaction_log
      • transports
      • tuning
      • uptime
      • user_id
      • version
      • views
  • AMPS Command Reference
    • Commands to AMPS
      • logon
      • Publishing
        • publish
        • delta_publish
      • Subscribing to and Querying Topics
        • subscribe
        • sow
        • sow_and_subscribe
        • unsubscribe
        • delta_subscribe
        • sow_and_delta_subscribe
      • Removing Messages (SOW/Topic or Message Queue)
      • heartbeat
      • flush
    • Responses from AMPS
      • sow: Content from Server
      • publish: Content from Server
      • oof: Content from Server
      • ack: Status from Server
      • group_begin / group_end : Result Set Delimiters
    • Protocol Reference
      • AMPS Protocol
      • Legacy Protocols Reference
    • Command Cookbook
      • Cookbook: Delta Publish
      • Cookbook: Delta Subscribe
      • Cookbook: Publish
      • Cookbook: SOW
      • Cookbook: SOW and Delta Subscribe
      • Cookbook: SOW and Subscribe
      • Cookbook: SOW Delete
      • Cookbook: Subscribe
  • Deployment Checklist
    • Ensure Sufficient Capacity
    • Apply System and AMPS Configuration
    • Create Maintenance Plan
    • Create Monitoring Strategy
    • Create Patch and Upgrade Plan
    • Create and Test Support Process
    • Conclusion
  • AMPS Clients
    • Performance Tips and Best Practices
    • C++
    • C#/.NET
    • Java
    • JavaScript
    • Python
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On this page
  • Header Fields
  • Options Field
  • Returns
  • TopicMatches
  • Matches
  • RecordsReturned
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  1. AMPS Command Reference
  2. Commands to AMPS
  3. Subscribing to and Querying Topics

sow

PrevioussubscribeNextsow_and_subscribe

Last updated 12 months ago

The sow command is used to query the contents of a previously defined topic in the SOW (including also views, queues, and conflated topics). A sow command can be used to query an entire SOW Topic, or a filter can be used to further refine the results from the SOW. For more information, see the and chapters in the AMPS User Guide.

Header Fields

Field

Description

Command

Command to be executed. Value: sow

Topic

The SOW topic from which the records will be queried.

AckType

Acknowledgment type for the given command.

Value is a comma separated list of one or more of the following: none, received, processed, completed or stats.

BatchSize

Number of records to return in a single sow query result message. The AMPS server default value is 1. It is recommended to use a higher value, as even small increases can yield greater performance in query result delivery. Current AMPS client libraries provide a BatchSize of 10 by default. The BatchSize header only applies to a sow query.

Bookmark

A bookmark specifying the historical state of the SOW to return results from. For SOW topics where historical query is enabled, AMPS returns the saved state of the SOW as of that bookmark. For SOW topics where historical query is not enabled, AMPS ignores this parameter.

CommandId

If specified with an AMPS command requesting an acknowledgment message, all requested acknowledgment messages will contain the CommandId in the ack response header.

Filter

Content filter expression. See the Content Filtering chapter in the AMPS User Guide for more information on using content filters.

OrderBy

Return the SOW results sorted by the specified fields.

Fields are a comma-delimited list of AMPS identifiers, and may optionally include a sort specifier, ASC or DESC.

QueryId

Unique identifier which is returned as part of the response delivered back to the client.

SowKeys

A comma-delimited list of SowKeys that identify the messages to return from the query.

TopN

Return up to the number of messages specified from the SOW query.

Options Field

The following table contains a list of the Options available and their definitions when used in the AMPS sow command.

Option

Description

none

This is the default Options type.

no_sowkey

Tells AMPS not to send the AMPS-generated SowKey for messages.

grouping=[keys]

For use with aggregated SOW queries.

The format of this option is a comma-delimited list of XPath identifiers within brackets. For example, to aggregate entries based on their /description (producing one record in the aggregation for each distinct value in /description), the value of this option would be: [/description]

This option must contain an entry for every field in the aggregated message. If there is no entry for a field in this option, that field will not appear in the aggregated message, even if the field is in the underlying message.

When this option is provided, a projection must also be provided.

When the topic has History enabled, this option can be used with a bookmark to aggregate the historical state of the SOW.

oof

Send on OOF message for records which have fallen out of focus from the original subscription.

projection=[fields]

For use with aggregated SOW queries.

Specifies a comma-delimited set of fields to project, within brackets. Each entry has the format described in the AMPS User Guide.

This option must contain an entry for every field in the aggregated message. If there is no entry for a field in this option, that field will not appear in the aggregated message, even if the field is in the underlying message.

There is no default for this option. When this option is provided, a grouping must also be provided.

When the topic has History enabled, this option can be used with a bookmark to aggregate the historical state of the SOW.

The maximum size of this option is 64KB.

replace

Replace the subscription associated with CmdId with another subscription.

When provided as part of sow_and_subscribe, AMPS runs a SOW query for the new subscription.

skip_n=n

Skips the number of messages specified before returning results.

A command that provides this option must also provide a top_n option (or header) and an OrderBy header.

top_n=n

Return up to the number of messages specified from the SOW query.

select=[fields]

Specifies the fields to include in messages provided on this subscription.

The contents of this option are a comma-delimited list of inclusion specifiers.

send_keys

AMPS will send the SOW keys (that is, the data fields used to identify unique messages in the SOW) back with matching messages from the SOW.

timestamp

AMPS will include a header with the time at which AMPS processed the incoming publish command for this message.

Returns

When a sow message is received, AMPS can return a received message as notification that the message has arrived. When the message filter has been processed, AMPS will return the processed acknowledgment message along with any errors that might have occurred.

The results returned by a SOW are put into a sow record group by first sending a group_begin message, followed by the matching SOW records. A group_end message is used to denote the close of query results processing.

The following table contains a listing of the acknowledgment messages supported by the sow command.

Acknowledgment

Description

none

No acknowledgment message is returned. This is the default behavior.

completed

The sow command has completed.

persisted

Not supported at this time.

processed

AMPS has compiled the filter(s) for the sow message.

received

The sow command has been received.

stats

Returns statistics related to the state of the SOW query results.

The stats message include three values in the header: Matches, TopicMatches, and the RecordsReturned. These are defined below:

TopicMatches

The total number of records compared across all matching SOW topics.

Matches

The number of records returned that match the topic regular expression and the content filter. This value can be greater than RecordsReturned in the case where the number of returned records is limited by TopN.

RecordsReturned

The total number of records returned to the client, which can be limited by the TopN header value.

Errors

Any errors which occur during a sow command are returned in the processed acknowledgment message. The error is identified in the Status header field in the acknowledgment message, and the reason given in the Reason header field.

The ordering of records returned by a SOW query is undefined unless the OrderBy header on the command is provided.

State of the World
SOW Queries