> On 7 Apr 2017, at 19:15, Jason Gordon <[email protected]> wrote: > > Hi Jan, > > You raise a good point. But it leads to another, similar question > > If rows 50 and 51 both contain a user with lastname Jackson, the recipe > says to use the following as the next key > > startkey=[02134,Jackson] endKey=[02134,{}] limit=51 startkey_doc_id=234 > (assuming _id for Jackson 234) > > but why not > > startkey=[02134] endKey=[02134,{}] startkey_doc_id=234 limit=51
because that produces a different result. views are sorted by key first, and only if keys are identical, those rows are sorted by doc_id. A document can occur in a view result multiple times, so you are not guaranteed to match the next page if you leave out the specific key that lead you to row 51. In your example with zip+lastname that’s less likely, but imagine docs with a list of tags: [‘red’, ‘green’, ‘blue’], now the same doc (id 234) shows up multiple times and in different parts of the overall view result. When you now do tag-by-zipcode, and your query, while paginating green, you would jump into row 51 or blue. Does that help? :) Best Jan -- > > Would they not accomplish the same thing? Is the 2nd query inefficient? > > Thanks, > > Jason > > > > > > > Jason Gordon | Principal | A S S U R E B R I D G E > Office: +1 888 409 6995 | Mobile: +1 978 885 6102 | Fax: +1 888 409 > 6995 > Email: [email protected] > > On Fri, Apr 7, 2017 at 5:32 AM, Jan Lehnardt <[email protected]> wrote: > >> >>> On 6 Apr 2017, at 21:18, Jason Gordon <[email protected]> >> wrote: >>> >>> The CouchDB docs 6.2.5 pagination recipe recommends to use the >>> "startkey_docid for pagination if, and only if, the extra row you fetch >> to >>> find the next page has the same key as the current startkey" >>> >>> Why can't you keep the start key the same and just keep updating the >>> startkey_docid? >>> >>> For example: >>> >>> if a view emits a key of [doc.zipcode, doc.lastname] >>> >>> And I'm looking for all people in a given zipcode. >>> and I do an initial query with startkey=[02134] endKey=[02134,{}] >> limit=51 >>> >>> the 50th user has a last name of Jackson (_id 123) and the 51st user >> has a >>> lastname of Johnson (_id 234). >>> >>> I could ask for the next page in two ways: >>> >>> *startkey=[02134,Johnson] endKey=[02134,{}] limit=51* >>> >>> OR >>> >>> *startkey=[02134] endKey=[02134,{}] startkey_doc_id=234 limit=51* >>> >>> Is there something wrong with the second approach? Would it perform >> poorly? >> >> What if lastname in row 51 is also Jackson? :) >> >> Best >> Jan >> -- >> >>> >>> Thanks >>> >>> Jason >>> >>> >>> Jason Gordon | Principal | A S S U R E B R I D G E >>> Office: +1 888 409 6995 | Mobile: +1 978 885 6102 | Fax: +1 888 409 >>> 6995 >>> Email: [email protected] >> >> -- >> Professional Support for Apache CouchDB: >> https://neighbourhood.ie/couchdb-support/ >> >> -- Professional Support for Apache CouchDB: https://neighbourhood.ie/couchdb-support/
