Multiple queryTask operations with maxRecordCount

Question

I tried searching but was surprised to not find any good results. Does anyone have a coding pattern to handle "paging" through a large query that exceeds the service's maxRecordCount property? I'd like to find a way to query the record count first, then build a bunch of query tasks with varying start and num properties to retrieve all the results. Promise.all() seems like it'd be what's needed but I can't quite wrap my head around how to make it all work. Here's my related question regarding distinct values that started this.

rscheitlin · Answer

Blake,

You can use QueryTask.exectueForCount() and in the Query object you can use returnDistinct. This will allow you to get a number that is in fact the real distinct count for your query. You then can decide if you need to use the paging route. Also the query result returns a exceededTransferLimit property that tells you if your results are not all the distinct data.

blake.terhune · Answer

Interesting approach, thanks. My feature layer (hosted at 10.5.1) doesn't have a maxRecordCount property. It doesn't even have a capabilities property. Any thoughts on that? After posting I got something that I think works. Besides the fact it doesn't work with returnDistinctValues (as I mentioned before), I'm not sure how I feel about it. var maxRecordCount = 1000; var queryTask = new QueryTask(); queryTask.url = 'http://server/arcgis/rest/services/ServiceName/MapServer/0'; var queryParams = new Query({ returnGeometry: false, outFields: ['someFieldName'], where: 'someFieldName is not null', }); queryTask.executeForCount(queryParams) .then(function(queryRecordCount) { var pageCount = Math.ceil(queryRecordCount / maxRecordCount); var resultPages = []; for (var i = 0; i < pageCount; i++) { resultPages.push(i * maxRecordCount); } return Promise.all(resultPages.map(function(resultPageStart){ queryParams.start = resultPageStart; queryParams.num = maxRecordCount - 1; return queryTask.execute(queryParams); })) }) .then(function(featureSets) { // collect features from each FeatureSet var features = []; featureSets.forEach(function(featureSet) { features = features.concat(featureSet.features); }) // do something with array of features }) .catch(function(err) { console.error(err); });‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

rscheitlin · Answer

Blake, Here is how I do that: var iMaxRecords = 0; var featuresProcessed = 0; var featuresTotal = 0; var maxRecordCount = layer.maxRecordCount; //normally 1000 queryTask = new QueryTask(uri); var cntQuery = new Query(); cntQuery.where = "1=1"; queryTask.executeForCount(cntQuery, function(count){ featuresTotal = count; if(count <= maxRecordCount){ //not an issue where you need to page }else{ query.returnGeometry = false; query.objectIds = null; query.where = "1=1"; queryTask.executeForIds(query, onSearchIdsFinish, onSearchError); } }); function onSearchIdsFinish(results){ if (results.length > 0) { objectIdsArray = results; featuresTotal = objectIdsArray.length; query.where = null; query.text = null; query.objectIds = objectIdsArray.slice(0, maxRecordCount); queryTask.execute(query, onSearchFinish, onSearchError); } else { console.error('onSearchIdsFinish returned zero length'); isQuerying = false; esc = false; } }‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ function onSearchFinish(featureSet) { // do something with the results featuresProcessed += featureSet.features.length; if (iMaxRecords === 0) { iMaxRecords = featuresProcessed; iStart += iMaxRecords; } if (iStart < objectIdsArray.length) { //If we get this far we need to requery the server for the next lot of records query.objectIds = objectIdsArray.slice(iStart, iStart + iMaxRecords); queryTask.execute(query, onSearchFinish, onSearchError); iStart += iMaxRecords; } }‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍