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

Pagination over fragments 

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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 pagpage. 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


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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

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layer. 

QueryDescription
SELECT id FROM anchor order by id LIMIT : pageSize OFFSET : (pageIndex -1) *  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.