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Jira Refs: CPS-1605 - Getting issue details... STATUS

Background

To query large outputs or large number of fragments across all anchors, we need to provide pagination for Query API( query data nodes across all anchors). it will help client to fetch limited set of data per request. below is two possible solutions for further discussions to decide appropriate choice.  

Issues and Decisions

#IssuesNotesDecision
1How to support pagination.we need to decide on how to support pagination for query API from two possible alternatives given below (pagination over fragments or pagination over anchors)
2Default page sizeshould we go with some default page size or query all records if pagination parameter in not provided. 

Pagination over fragments 

Implementation

API : GET http://<IP>:<PORT>/cps/api/v2/dataspaces/{dataspace-name}/nodes/query?cps-path={cps-path}&descendants={descendants}&pageIndex={pageIndex}&pageSize={pageSize}

Request Parameters:

ParameterisRequiredDescription
cps-pathyesnode path to be queried
descendantsnoNumber of descendants to be queried. default is none..
pageIndexnopage index starting from 1. default is -1 for all records.
resultSizenonumber of fragments per pag. default is -1 for all fragments..

Query

QueryDescription
SELECT id, anchor_id AS anchorId, xpath, parent_id AS parentId, CAST(attributes AS TEXT) AS attributes FROM FRAGMENT WHERE xpath ~ :xpathRegex ORDERED BY id LIMIT :resultSize OFFSET  (:resultIndex - 1) * :resultSize Query limited fragments in order of fragment id


Pagination over anchors

we can provide pagination over anchors where client can choose number of anchors per request to fetch fragments from. 

Implementation

API : GET http://<IP>:<PORT>/cps/api/v2/dataspaces/{dataspace-name}/nodes/query?cps-path={cps-path}&descendants={descendants}&pageIndex={pageIndex}&pageSize={pageSize}

Request Parameters:

ParameterisRequiredDescription
cps-pathyesnode path to be queried
descendantsnoNumber of descendants to be queried. default is none
pageIndexnopage index starting from 1. default is -1 for all pages(all anchors)
pageSizenonumber of records per request. It is nothing but number of anchors to be queried. Default is -1 for all pages(all anchors)

Response Headers

Headerdescription
totalResultstotal number of available records (achors)
totalPagestotal nulber of pages.

Response body

FormatExample

[

{"anchorName":"anchor-01",

"dataNodes":[{data-tree1},...{data-tree-n}]

...

,{"anchorName":"anchor-02",

"dataNodes": [{datatree1},...,{data-tree-n}]

}

]

Example 
[
   {
      "anchorName":"anchor01",
      "dataNodes":[
         {
            "test:bookstore":{
               "bookstore-name":"Chapters",
               "categories":[
                  {
                     "code":1,
                     "name":"SciFi"
                  }
               ]
            }
         }
      ]
   },
   {
      "anchorName":"anchor02",
      "dataNodes":[
         {
            "test:bookstore":{
               "bookstore-name":"store01",
               "categories":[
                  {
                     "code":2,
                     "name":"SciFi"
                  }
               ]
            }
         }
      ]
   }
]

Query executed in persistence layer 

QueryDescription
SELECT id FROM anchor order by id LIMIT : pageSize OFFSET : (pageIndex -1) *  pageSize query list of anchors 
SELECT id, anchor_id AS anchorId, xpath, parent_id AS parentId, CAST(attributes AS TEXT) AS attributes FROM FRAGMENT WHERE anchor_id IN :anchorList AND xpath ~ :xpathRegexquery fragments for list of anchors from above query
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