[jira] [Commented] (OAK-1263) optimize oak index to support 'fast ORDER BY' queries to support sorting & pagination for large set of children

["Thomas Mueller (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-1263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13919181#comment-13919181 ] 

Thomas Mueller commented on OAK-1263:
-------------------------------------

Your new patch still has some unnecessary formatting changes, for example the very first lines of the patch, IndexUtils. getOrCreateOakIndex.

Some more comments: 

It looks like you are using 3 spaces indentation, while in Oak we use 4 spaces. Could you use 4 spaces as well please?

Some lines are over 200 characters long. Could we use a line length of 100 characters (the Eclipse default is 80, and Google uses 80 or 100)? Some if the long lines are due to formatting changes of existing code.

{noformat}
if(Strings.isNullOrEmpty(value)){
{noformat}

Could you use the following instead (Eclipse and Google code conventions):

{noformat}
if (Strings.isNullOrEmpty(value)) {
{noformat}

Other spacing is inconsistent, for example:

{noformat}
+            pns = Collections.singleton(value);
+            this.properlyConfigured=true;   
{noformat}

Could you use the following:

{noformat}
+            pns = Collections.singleton(value);
+            this.properlyConfigured = true;   // <= spaces
{noformat}

Could you use spaces before commas?

{noformat}
+    /**
+     * retrieve the type of the index
+     * 
+     * @return
+     */
{noformat}

I would prefer the following:

{noformat}
+    /**
+     * Retrieve the type of the index.
+     * 
+     * @return the type
+     */
{noformat}


> optimize oak index to support 'fast ORDER BY' queries to support sorting & pagination for large set of children
> ---------------------------------------------------------------------------------------------------------------
>
>                 Key: OAK-1263
>                 URL: https://issues.apache.org/jira/browse/OAK-1263
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: query
>    Affects Versions: 0.12
>            Reporter: Stefan Egli
>            Assignee: Alex Parvulescu
>             Fix For: 0.18
>
>         Attachments: OAK-1263-r1.patch, OAK-1263-r1a.patch, benchmark-20140228112150.log, benchmark-20140228120718.log, benchmark-20140228125248.log
>
>
> We have a use case where we'd like to be able to use an index in a "pagination-like" fashion. That is, we'd like to be able to have an index on a subtree on a certain property, and then run a query which does ORDER BY that property combined with OFFSET. That way, essentially allowing pagination of child nodes of a particular parent based on 'sorted by a certain property'.
> AFAIU currently the oak index is not optimized to support ORDER BY queries in a fast manner. The index keeps 'the child nodes unsorted', ie to process an ORDER BY, the child nodes would have to be 'manually sorted' which can result in bad performance given a large number of child nodes.



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