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Table of Contents

Jira Refs:

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serverSystem Jira
columnIdsissuekey,summary,issuetype,created,updated,duedate,assignee,reporter,priority,status,resolution
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serverId4733707d-2057-3a0f-ae5e-4fd8aff50176
keyCPS-1605

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 are 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)

it was discussed in weekly meeting and decided by team members to implement pagination over anchors. 

2Default page sizeshould we go with some default page size or query all records if pagination parameter in not provided. 

By default if pagination parameter in not provided then query all records.

Pagination over fragments 

...

ParameterisRequiredDescription
cps-pathyesnode path to be queried.
descendantsnoNumber of descendants to be queried. default is none.
resultIndexpageIndexnopage index starting from 1. . default is -1 for all records.
resultSizenonumber of fragments per page starting from 1 (TBD). . default is -1 for all fragments.

Query

QueryDescriptionDecision 
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


...

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

Request Parameters:

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

Response Headers

Headerdescription
totalAnchors
totalPages
total number of anchorsresultIndexrequested index of anchoranchorSizerequested number of anchors

Query

QueryDescriptionDecision
Total number of pages for given page size

Response body

FormatExample

[

{"anchorName":"anchor-01",

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

...

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

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

}

]


Code Block
titleExample
collapsetrue
[
   {
      "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 : anchorSize pageSize OFFSET : (resultIndex pageIndex -1) * :anchorSize   pageSize query list of anchors 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.