Azure Mobile Services Node.js update column field count during read query - azure-mobile-services

Question

I would like to update a column in a specific row in Azure Mobile Services using server side code (node.js).
The idea is that the column A (that stores a number) will increase its count by 1 (i++) everytime a user runs a read query from my mobile apps.
Please, how can I accomplish that from the read script in Azure Mobile Services.
Thanks in advance,

Answer 1

Check out the examples in the online reference. In the table Read script for the table you're tracking you will need to do something like this. It's not clear whether you're tracking in the same table the user is reading, or in a separate counts table, but the flow is the same.
Note that if you really want to track this you should log read requests to another table and tally them after the fact, or use an external analytics system (Google Analytics, Flurry, MixPanel, Azure Mobile Engagement, etc.). This way of updating a single count field in a record will not be accurate if multiple phones read from the table at the same time -- they will both read the same value x from the tracking table, increment it, and update the record with the same value x+1.
function read(query, user, request) {
var myTable = tables.getTable('counting');
myTable.where({
tableName: 'verses'
}).read({
success: updateCount
});
function updateCount(results) {
if (results.length > 0) {
// tracking record was found. update and continue normal execution.
var trackingRecord = results[0];
trackingRecord.count = trackingRecord.count + 1;
myTable.update(trackingRecord, { success: function () {
request.execute();
});
} else {
console.log('error updating count');
request.respond(500, 'unable to update read count');
}
}
};
Hope this helps.
Edit: fixed function signature and table names above, adding another example below
If you want to track which verses were read (if your app can request one at a time) you need to do the "counting" request and update after the "verses" request, because the script doesn't tell you up front which verse records the user requested.
function read(query, user, request) {
request.execute( { success: function(verseResults) {
request.respond();
if (verseResults.length === 1) {
var countTable = tables.getTable('counting');
countTable.where({
verseId: verseResults[0].id
}).read({
success: updateCount
});
function updateCount(results) {
if (results.length > 0) {
// tracking record was found. update and continue normal execution.
var trackingRecord = results[0];
trackingRecord.count = trackingRecord.count + 1;
countTable.update(trackingRecord);
} else {
console.log('error updating count');
}
}
}
});
};
Another note: make sure your counting table has an index on the column you're selecting by (tableName in the first example, verseId in the second).