Wikiservice: Refresh MemCP documentation: accuracy, operational guidance, performance profile and maintained API reference

2026-08-28T09:59:22Z

Refresh MemCP documentation: accuracy, operational guidance, performance profile and maintained API reference

← Older revision		Revision as of 11:59, 28 August 2026
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	~~← Back to~~ [[Full SCM API documentation]]		<!-- Copyright (C) 2026 Carl-Philip Haensch -->
			<!-- SPDX-License-Identifier: GPL-3.0-or-later -->

			<span id="window-functions"></span>
			= Window Functions =

			<!-- Generated from MemCP c42e19eba on 2026-08-27; do not edit manually. -->
			<div class="mw-message-box mw-message-box-notice">Generated from MemCP commit <code>c42e19eba</code> on 27 August 2026. See [[Full SCM API documentation]].</div>

			The '''Window Functions''' runtime helpers support ordered streaming plans. They emit complete producer values, apply bounded serial reductions, maintain ring-buffer frames, and flush pending window positions.

			SQL users normally call <code>ROW_NUMBER</code>, <code>RANK</code>, <code>LEAD</code>, <code>LAG</code>, and related SQL functions rather than invoking these helpers directly. The planner may stream a frame or use an ordered-reduce computed column depending on ordering and reuse.

	== stream_emit ==		== stream_emit ==
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	=== Parameters ===		=== Parameters ===

	* '''emit''' (<code>func(~~value:~~any) ~~->~~ any</code>):		* '''emit''' (<code>func</code>)
	* '''value''' (<code>any</code>):		** '''Parameters'''
			*** '''value''' (<code>any</code>)
			** '''Returns'''
			*** '''value''' (<code>any</code>)
			* '''value''' (<code>any</code>)

	<span id="returns"></span>		<span id="returns"></span>
	=== Returns ===		=== Returns ===

	<code>any</code>		* '''value''' (<code>any</code>)

	== stream_window_reduce ==		== stream_window_reduce ==
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	* '''offset''' (<code>number</code>): number of complete producer values to skip		* '''offset''' (<code>number</code>): number of complete producer values to skip
	* '''limit''' (<code>number</code>): maximum values to reduce, or -1 for no limit		* '''limit''' (<code>number</code>): maximum values to reduce, or -1 for no limit
	* '''reduce''' (<code>func(~~acc:~~any, value:any) ~~->~~ any</code>)~~: serial accumulator over complete values~~		* '''reduce''' (<code>func</code>): serial accumulator over complete values
			** '''Parameters'''
			*** '''acc''' (<code>any</code>)
			*** '''value''' (<code>any</code>)
			** '''Returns'''
			*** '''value''' (<code>any</code>)
	* '''neutral''' (<code>any</code>): initial accumulator		* '''neutral''' (<code>any</code>): initial accumulator
	* '''producer''' (<code>func~~(emit:func) -> any~~</code>): nested streaming plan called with a one-value emit callback		* '''producer''' (<code>func</code>): nested streaming plan called with a one-value emit callback
			** '''Parameters'''
			*** '''emit''' (<code>func</code>): emits one complete value
			**** '''Parameters'''
			***** '''value''' (<code>any</code>)
			**** '''Returns'''
			***** '''result''' (<code>any</code>)
			** '''Returns'''
			*** '''value''' (<code>any</code>)

	<span id="returns-1"></span>		<span id="returns-1"></span>
	=== Returns ===		=== Returns ===

	<code>any</code>		* '''value''' (<code>any</code>)

	== window_mut ==		== window_mut ==
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	* '''window''' (<code>list</code>): ring buffer accumulator		* '''window''' (<code>list</code>): ring buffer accumulator
	* '''emit_fn''' (<code>func~~(values:any...) -> any~~</code>): callback receiving all window values oldest-to-newest		* '''emit_fn''' (<code>func</code>): callback receiving all window values oldest-to-newest
			** '''Parameters'''
			*** '''values''' (<code>any</code>) ''(variadic)''
			** '''Returns'''
			*** '''value''' (<code>any</code>)
	* '''vals''' (<code>list</code>): list of stride values to insert		* '''vals''' (<code>list</code>): list of stride values to insert

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	=== Returns ===		=== Returns ===

	<code>list</code>		* '''value''' (<code>list</code>)

	== window_flush ==		== window_flush ==
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	* '''window''' (<code>list</code>): ring buffer accumulator		* '''window''' (<code>list</code>): ring buffer accumulator
	* '''emit_fn''' (<code>func~~(values:any...) -> any~~</code>): callback receiving all window values oldest-to-newest		* '''emit_fn''' (<code>func</code>): callback receiving all window values oldest-to-newest
			** '''Parameters'''
			*** '''values''' (<code>any</code>) ''(variadic)''
			** '''Returns'''
			*** '''value''' (<code>any</code>)
	* '''count''' (<code>number</code>): number of nil positions to shift in		* '''count''' (<code>number</code>): number of nil positions to shift in

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	=== Returns ===		=== Returns ===

	<code>nil</code>		* '''value''' (<code>nil</code>)

	== show_processlist ==		== show_processlist ==
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	=== Returns ===		=== Returns ===

	<code>list</code>		* '''value''' (<code>list</code>)

	== connection_id ==		== connection_id ==
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	=== Returns ===		=== Returns ===

	<code>int</code>		* '''value''' (<code>int</code>)

	== kill_query ==		== kill_query ==
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	=== Returns ===		=== Returns ===

	<code>bool</code>		* '''value''' (<code>bool</code>)

Carli: Created page with "← Back to Full SCM API documentation == stream_emit == invokes a streaming callback immediately; marks ordering-sensitive emission as an observable effect '''Allowed number of parameters:''' 2–2 === Parameters === * '''emit''' (`func(value:any) -> any`): * '''value''' (`any`): === Returns === `any` == stream_window_reduce == applies OFFSET/LIMIT and a serial redu..."

2026-08-27T06:38:43Z

Created page with "← Back to Full SCM API documentation == stream_emit == invokes a streaming callback immediately; marks ordering-sensitive emission as an observable effect '''Allowed number of parameters:''' 2–2 === Parameters === * '''emit''' (<code>func(value:any) -> any</code>): * '''value''' (<code>any</code>): === Returns === <code>any</code> == stream_window_reduce == applies OFFSET/LIMIT and a serial redu..."

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← Back to [[Full SCM API documentation]]

== stream_emit ==

invokes a streaming callback immediately; marks ordering-sensitive emission as an observable effect

'''Allowed number of parameters:''' 2–2


=== Parameters ===

* '''emit''' (<code>func(value:any) -> any</code>):
* '''value''' (<code>any</code>):


=== Returns ===

<code>any</code>

== stream_window_reduce ==

applies OFFSET/LIMIT and a serial reducer to complete values emitted by a nested streaming producer without collecting an intermediate relation

'''Allowed number of parameters:''' 5–5


=== Parameters ===

* '''offset''' (<code>number</code>): number of complete producer values to skip
* '''limit''' (<code>number</code>): maximum values to reduce, or -1 for no limit
* '''reduce''' (<code>func(acc:any, value:any) -> any</code>): serial accumulator over complete values
* '''neutral''' (<code>any</code>): initial accumulator
* '''producer''' (<code>func(emit:func) -> any</code>): nested streaming plan called with a one-value emit callback


=== Returns ===

<code>any</code>

== window_mut ==

Ring buffer shift-insert for window functions. (window_mut window emit_fn vals) writes vals (a list of stride values) into the current slot, increments counter. If skip>0, decrements skip. Otherwise calls (emit_fn oldest_v0 oldest_v1 ... newest_v0 newest_v1) with all slot values ordered oldest-to-newest. Returns updated window.

'''Allowed number of parameters:''' 3–3


=== Parameters ===

* '''window''' (<code>list</code>): ring buffer accumulator
* '''emit_fn''' (<code>func(values:any...) -> any</code>): callback receiving all window values oldest-to-newest
* '''vals''' (<code>list</code>): list of stride values to insert


=== Returns ===

<code>list</code>

== window_flush ==

Flush remaining window buffer by shifting in nils. (window_flush window emit_fn count) shifts in count positions of nils, calling emit_fn for each displaced position. Returns nil.

'''Allowed number of parameters:''' 3–3


=== Parameters ===

* '''window''' (<code>list</code>): ring buffer accumulator
* '''emit_fn''' (<code>func(values:any...) -> any</code>): callback receiving all window values oldest-to-newest
* '''count''' (<code>number</code>): number of nil positions to shift in


=== Returns ===

<code>nil</code>

== show_processlist ==

returns a list of active sessions for SHOW [FULL] PROCESSLIST; pass true for full info

'''Allowed number of parameters:''' 0–1


=== Parameters ===

* '''full''' (<code>bool</code>): if true, include full Info text ''(optional)''


=== Returns ===

<code>list</code>

== connection_id ==

returns the process-list ID of the current session (MySQL CONNECTION_ID() equivalent)

'''Allowed number of parameters:''' 0–0


=== Parameters ===

''This function has no parameters.''


=== Returns ===

<code>int</code>

== kill_query ==

cancel the running query in session id; returns true if a query was killed

'''Allowed number of parameters:''' 1–1


=== Parameters ===

* '''id''' (<code>int</code>): session ID from SHOW PROCESSLIST


=== Returns ===

<code>bool</code>

Window Functions - Revision history

Wikiservice: Refresh MemCP documentation: accuracy, operational guidance, performance profile and maintained API reference