Subclauses CIP #200

Mats-SX · 2017-03-06T14:22:41Z

This CIP is in response to #194

petraselmer

Nice one! Just a few comments

petraselmer · 2017-03-06T14:39:31Z

cip/1.accepted/CIP2017-03-01-SKIP-and-LIMIT.adoc

+
+== Background
+
+This CIP is a proposal in answer to link:https://github.com/opencypher/openCypher/issues/194[CIR-2017-194].


"answer" -> "response"

petraselmer · 2017-03-06T14:48:32Z

cip/1.accepted/CIP2017-03-01-SKIP-and-LIMIT.adoc

+=== Semantics
+
+The `LIMIT` subclause prevents records passing through its parent clause after the specified amount of rows, as determined by the limit expression, has been processed.
+For these semantics to be well defined, the limit expression must be constant over the query lifetime, such as parameters or literals.


Can this be expanded on a bit more? It's not 100% clear what is being said. If need be, an example could be provided.

Expanded and gave two examples.

petraselmer · 2017-03-06T14:50:04Z

cip/1.accepted/CIP2017-03-01-SKIP-and-LIMIT.adoc

+
+==== Updating queries
+
+The use of `LIMIT` opens the possibility for certain performance optimisations.


"opens the possibility" -> "opens up the possibility"

petraselmer · 2017-03-06T14:52:34Z

cip/1.accepted/CIP2017-03-01-SKIP-and-LIMIT.adoc

+
+=== Semantics
+
+The `LIMIT` subclause prevents records passing through its parent clause after the specified amount of rows, as determined by the limit expression, has been processed.


"limit expression" -> hmmm... it reads a bit awkwardly at present. Maybe something such as "expression provided to the LIMIT clause" or something. Maybe even formatting would help, such as all in italics, or LIMIT expression?

How about

the expression used as argument to LIMIT

?

That works - just include "the argument"

petraselmer · 2017-03-06T14:53:52Z

cip/1.accepted/CIP2017-03-01-SKIP-and-LIMIT.adoc

+==== Updating queries
+
+The use of `LIMIT` opens the possibility for certain performance optimisations.
+Clauses that come early in the query do not have to be evaluated over the full dataset, just enough to reach the subsequent limit.


"that come early" -> "appearing earlier"

"do not have to be evaluated over the full dataset, just enough to reach the subsequent limit."
->
"only need to be evaluated until the limit is reached, as opposed to evaluating the entire dataset."

petraselmer · 2017-03-06T14:58:25Z

cip/1.accepted/CIP2017-03-01-SKIP-and-LIMIT.adoc

+Clauses that come early in the query do not have to be evaluated over the full dataset, just enough to reach the subsequent limit.
+These optimisations are however not always applicable in combination with updating clauses.
+Semantics between clauses is defined such that _all_ of a previous clause is processed (logically) before _any_ of a subsequent clause is processed.
+This means that _all_ side effects must happen before a `LIMIT` is allowed to halt the processing of records in preceding clauses.


"halt" -> "terminate"

petraselmer · 2017-03-06T14:58:48Z

cip/1.accepted/CIP2017-03-01-SKIP-and-LIMIT.adoc

+Semantics between clauses is defined such that _all_ of a previous clause is processed (logically) before _any_ of a subsequent clause is processed.
+This means that _all_ side effects must happen before a `LIMIT` is allowed to halt the processing of records in preceding clauses.
+
+Consider the below query:


"below query"
->
"following query"

petraselmer · 2017-03-06T14:59:21Z

cip/1.accepted/CIP2017-03-01-SKIP-and-LIMIT.adoc

+
+Consider the below query:
+
+.Create a producer for each item, return first 100 product ids.


Format "producer"

"item, return first 100 product ids"
->
"item, returning the first 100 product ids"

I don't think producer needs formatting here. The example talks about items and producers as concepts, and I think it's clear that these are then represented by nodes with matching labels.

petraselmer · 2017-03-06T15:01:23Z

cip/1.accepted/CIP2017-03-01-SKIP-and-LIMIT.adoc

+
+If the user intention is to only do a partial update of the graph, the query must be rewritten:
+
+.Create a producer for the 100 first items, return their product ids.


"100 first items, return their product ids"
->
"top 100 items, and return their product ids"

Format "producer"

- Rename file to correct name for the CIP - Improve language

thobe

This should be extended to also include ORDER BY, and SKIP.

In fact all of the following sub-clauses should always go together:

WHERE
ORDER BY
SKIP
LIMIT

Mats-SX · 2017-03-31T09:33:04Z

@thobe Extended!

Mats-SX added the CIP label Mar 6, 2017

Add the LIMIT CIP

2967f79

Fixes opencypher#194

Mats-SX force-pushed the limit-cip branch from 7f10456 to 2967f79 Compare March 6, 2017 14:23

petraselmer suggested changes Mar 6, 2017

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petraselmer approved these changes Mar 8, 2017

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Add example for how only constant expressions are allowed

3a3f198

- Rename file to correct name for the CIP - Improve language

Mats-SX force-pushed the limit-cip branch from 60344fe to 3a3f198 Compare March 8, 2017 11:24

thobe suggested changes Mar 30, 2017

View reviewed changes

Mats-SX added 2 commits March 31, 2017 09:57

Change title to Subclauses

aa6a008

Add SKIP, WHERE and ORDER BY

2343256

Mats-SX changed the title ~~Add the LIMIT CIP~~ Add the Subclauses CIP Mar 31, 2017

Reorder subclauses to be consistent with grammar order

5339768

Mats-SX changed the title ~~Add the Subclauses CIP~~ Subclauses CIP May 5, 2017

Reformatted title

3369038

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Subclauses CIP #200

Subclauses CIP #200

Mats-SX commented Mar 6, 2017 •

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Mats-SX commented Mar 31, 2017


		== Background

		This CIP is a proposal in answer to link:https://github.com/opencypher/openCypher/issues/194[CIR-2017-194].


		==== Updating queries

		The use of `LIMIT` opens the possibility for certain performance optimisations.


		=== Semantics

		The `LIMIT` subclause prevents records passing through its parent clause after the specified amount of rows, as determined by the limit expression, has been processed.


		Consider the below query:

		.Create a producer for each item, return first 100 product ids.


		If the user intention is to only do a partial update of the graph, the query must be rewritten:

		.Create a producer for the 100 first items, return their product ids.

Subclauses CIP #200

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Subclauses CIP #200

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Mats-SX commented Mar 31, 2017

Mats-SX commented Mar 6, 2017 •

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