Couchbase Nodes

Read and write Couchbase documents by key, with optimistic locking through CAS, and query them with read-only SQL++.

Operations

Get · Upsert · Replace · Remove Document · Run Query

Locking

CAS, delivered and taken as text

Query

Read-only, parameters as values, Max Rows applied by Couchbase

Couchbase keeps JSON documents in collections of a bucket. MaestroHub provides five nodes: four that work on one document by its key, and Run Query for SQL++. All use a Couchbase connection, which names the bucket; each function names its scope and collection.

Configuration Quick Reference

Field	What you choose	Details
Parameters	Connection, Function, Function Parameters, Timeout Override	Select the connection profile, function, configure function parameters with expression support, and optionally override timeout.
Settings	Description, Timeout (seconds), Retry on Timeout, Retry on Fail, On Error	Node description, maximum execution time, retry behavior on timeout or failure, and error handling strategy. All execution settings default to pipeline-level values.

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Couchbase Get Document Node

Couchbase Get Document Node

Function Name	Purpose	Common Use Cases
Get Document	Read the document at key in scope.collection, with its CAS	The latest state of a machine, a recipe or a work order by its ID; the read before a conditional Replace

A key with no document is a normal result with found false: branch on it rather than catching an error.

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Couchbase Upsert Document Node

Couchbase Upsert Document Node

Function Name	Purpose	Common Use Cases
Upsert Document	Write document to key, creating or overwriting it, with an optional expiry and durability level	One document per machine with its latest state, shift logs, configuration snapshots

Writing the same document to the same key again leaves the same state, so the node is eligible for store-and-forward: writes made while Couchbase is unreachable are applied in order per key when it returns.

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Couchbase Replace Document Node

Couchbase Replace Document Node

Function Name	Purpose	Common Use Cases
Replace Document	Overwrite the document at key only if it exists, and only at cas when one is given	Read-modify-write without overwriting a concurrent change: work orders, counters kept in a document

A CAS mismatch or a missing document fails the node and writes nothing. The node is never buffered by store-and-forward, because a CAS read before an outage would be stale by the time a replay ran.

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Couchbase Remove Document Node

Couchbase Remove Document Node

Function Name	Purpose	Common Use Cases
Remove Document	Remove the document at key, optionally only at cas	Closing a finished work order, clearing a buffer entry once it was forwarded

Removing a key with no document succeeds with removed false, so a repeated remove changes nothing.

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Couchbase Run Query Node

Couchbase Run Query Node

Function Name	Purpose	Common Use Cases
Run Query	Run the SQL++ statement in scope with its args, and return at most maxRows rows	Machines in alarm on a line, alarm counts before a decision, documents changed since a time

Every statement is sent read-only: Couchbase refuses one that writes. Values go as query parameters ($1 or $name), never spliced into the statement. At Max Rows the read stops and Couchbase ends the query; with Scan Consistency requestPlus the query sees every write made before it.

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Output

Every Couchbase node delivers its data under result, and execution facts (success, functionId, durationMs, timestamp) under _metadata:

Node	Expression	Description
Get Document	$node["Name"].result.key	The key that was read
	$node["Name"].result.found	Whether a document exists at that key
	$node["Name"].result.document	The document as stored, or null when found is false. $node["Name"].result.document.state reads a field
	$node["Name"].result.cas	Only when found: the document's CAS as decimal text, for a later Replace or Remove
Upsert Document, Replace Document	$node["Name"].result.key	The key that was written
	$node["Name"].result.cas	The document's new CAS as decimal text
Remove Document	$node["Name"].result.key	The key that was removed
	$node["Name"].result.removed	Whether a document was removed: false when none existed at the key
	$node["Name"].result.cas	Only when removed: the CAS of the removal as decimal text
Run Query	$node["Name"].result.rows	The rows as the query returned them: an object per row, or a bare value for SELECT RAW. $node["Name"].result.rows[0].machine reads a field
	$node["Name"].result.rowCount	How many rows were delivered
	$node["Name"].result.truncated	true when the query had more rows than Max Rows and the read stopped there

A CAS is a 64-bit number, larger than a JSON number holds exactly, so it is always text: pass it on as it is, never through arithmetic.

The call's own facts ride along under _metadata next to the four every connected node carries: _metadata.method (the operation), _metadata.connectionId, _metadata.protocol (couchbase) and _metadata.bucket on every node; _metadata.scope on every node, and _metadata.collection on the four document nodes; after Run Query, _metadata.maxRows, the row limit it ran with.