> ## Documentation Index
> Fetch the complete documentation index at: https://docs.e6data.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Spark Connect

> spark_connect

ReferenceApplies to: Unified engine deployments

`[spark_connect]`

## Listener

## Protocol limits

### `protocol.max_retained_operations`

Limits how many operations the server keeps available for client reattachment.

* **Default:** `64`
* **Type:** integer; positive

> **Example**
>
> `64` bounds retained operations for clients that reconnect. It does not mean a query can return only 64 rows.

### `protocol.max_retained_response_bytes`

Limits how much operation-response data is kept so it can be replayed to a reconnecting client.

* **Default:** `16777216`
* **Type:** integer (bytes); positive

> **Example**
>
> `16777216` gives retained response data a 16 MiB budget. The full stored query result has separate limits.

### `protocol.user_id`

Chooses the identity the Spark Connect listener assigns to client operations.

* **Default:** `"local"`
* **Type:** string

> **Example**
>
> Setting it to `"analytics"` uses that server-owned identity even if a client sends a different UserContext value.

### `protocol.max_request_bytes`

Limits the encoded size of one incoming request.

* **Default:** `16777216`
* **Type:** integer (bytes); positive

> **Example**
>
> `16777216` accepts a request up to 16 MiB. A large submitted plan or SQL request counts toward that request’s limit.

### `protocol.max_response_bytes`

Limits the encoded size of one outgoing response.

* **Default:** `68157440`
* **Type:** integer (bytes); positive

> **Example**
>
> `67108864` gives one response a 64 MiB budget. A larger result can require smaller result pages rather than one larger response.

### `protocol.max_plan_depth`

Limits how deeply an incoming client plan may be nested.

* **Default:** `128`
* **Type:** integer; positive

> **Example**
>
> `128` bounds nesting to 128 levels. Deeply nested expressions can reach this limit even when the SQL text is short.

### `protocol.max_plan_nodes`

Limits how many operations and expressions an incoming plan may contain.

* **Default:** `100000`
* **Type:** integer; positive

> **Example**
>
> `100000` bounds the plan’s node count. Raising the HTTP byte limit alone does not increase this count.


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