[GitHub] [druid] kfaraz commented on a diff in pull request #13228: docs(msq): update insert vs replace for dimension-based segment pruning

[GitBox <gi...@apache.org>]

kfaraz commented on code in PR #13228:
URL: https://github.com/apache/druid/pull/13228#discussion_r996247003


##########
docs/multi-stage-query/concepts.md:
##########
@@ -102,6 +104,19 @@ issues](./known-issues.md#select) page.
 
 For more information about the syntax, see [REPLACE](./reference.md#replace).
 
+When deciding whether to use REPLACE or INSERT, keep in mind that REPLACE can perform dimension-based segment pruning but INSERT cannot. To use dimension-based segment pruning, your query needs to meet the following requirements:

Review Comment:
   This part and the above change on line 81/82 needs to be rephrased.
   
   To clarify, INSERT or REPLACE queries (better called statements for less ambiguity in this case?) cannot and need not perform dimension-based pruning (* unless they are doing a sub-SELECT on some other datasource).
   It is the queries (i.e. SELECT queries of any kind) that we run on the _segments_ generated with the above INSERT or REPLACE statements that could potentially benefit from such pruning.
   
   As a suggestion:
   
   ```suggestion
   When deciding whether to use REPLACE or INSERT, keep in mind that segments generated with REPLACE can be pruned with dimension-based pruning but those generated with INSERT cannot. Please refer to [Clustering](#clustering) for the prerequisites of dimension-based pruning.:
   ```



##########
docs/multi-stage-query/concepts.md:
##########
@@ -102,6 +104,19 @@ issues](./known-issues.md#select) page.
 
 For more information about the syntax, see [REPLACE](./reference.md#replace).
 
+When deciding whether to use REPLACE or INSERT, keep in mind that REPLACE can perform dimension-based segment pruning but INSERT cannot. To use dimension-based segment pruning, your query needs to meet the following requirements:
+
+- Segments were generated by a REPLACE statement, not an INSERT statement.

Review Comment:
   I don't think this section needs to be reiterated here as this info is already captured later in the "Clustering" section. I think just linking to that section is enough.



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