Fetch latest record / entry in Deta base?

[TychoLex42]

Quick question: How would I retrieve the latest entry/record in the Deta Base? Based on a date is not possible, right? Or based on the key? Sorry for being fairly new to this! Thanks so much for helping me and building this awesome tool!

[xeust]

Hi @TychoLex42 , Base will return items using fetch in ascending order, so you can indeed do this, using a variation of unix timestamps as keys.

If you simply use unix timestamps as keys, this will do the opposite of what you want -- as the first item you fetch will be the oldest item (smallest time stamp).

So what you can do, is use keys that that get smaller as unix time gets larger. So if you store items with the key scheme some really big number - unix time stamp, the first item you get from a fetch will be the most recent.

Hope that helps!

[xeust]

Hi @TychoLex42 ,

You'll actually want to keep the bigNumer constant -- this guarantees that your keys will be getting smaller the later you store them (since fetch returns in ascending order). If you increase bigNumber with each new item, you'd break the guarantee that keys get smaller with time.

Here's a simple express server that should do what you want:

const express = require('express');
const { Deta } = require('deta');

const app = express(); 

const deta = Deta(); 

const db = deta.Base('simple_db'); 

const bigNumber = 8.64e15;

const generateKey = (timestamp) => {
	return `${ bigNumber -  timestamp}`
}

app.get('/', async (req, res) => {
    const timestamp = Date.now();
    const data = {'key': generateKey(timestamp), 'timestamp': Date(timestamp).toString()}
    await db.put(data);
    res.send('Hello World!');
})

module.exports = app;

Each time you hit the endpoint, a new item is stored in your Base under the key scheme of bigNumer - Date.now(). I've also stored Date.now() in human readable format next to the key. If you load up your Base's UI, you'll see that the most recent item stored (expand the timestamp field) is always the first item returned via fetch:

(One small note -- if you're expecting to store multiple items in the same millisecond, you'll want to append the key scheme with a bit more information to prevent a collision of keys).

Please let me know if you can't get what you want working.

[TychoLex42]

Hey @xeust,
thanks so much again for your long and detailed reply.
I now know what I understood wrong in your previous answer. I thought that your suggestion of some really big number - unix time stamp was meant to be a string, e.g. "9999 - 2022-07-28 15:13". But I know get that you suggested to subtract the timestamp from the large number! My logic was flawed and I should have read your answer more carefully!
I know get it that the large number has to stay the same, as the time stamp gets "higher".
Thanks again for your help! :-)

[xeust]

Hi @TychoLex42 -- no problem :)

[chandrashekarcn]

make one entry with key new_rec and every time you put data in base updte new_rec with that key.

ex:
create one record as below
{key:new_rec,last:timestamp}

every time when you put deta in detabase update{key:new_rec, last:timestamp(new entry) }

[Sokhavuth]

I would pull all documents from Deta Base first. The result is a JS array of objects. So we can use vanilla JavaScript sort() method to sort this array of objects by date. The result we can get the newest or the oldest record by date.

let result = await mydb.posts.fetch(query)
let allItems = result.items

while(result.last){
       result = await mydb.posts.fetch(query, {last: result.last})
       allItems = allItems.concat(result.items)
}

allItems.sort((a, b) => {     
    let da = new Date(a.date)
    let db = new Date(b.date)
    return db - da
})
        
const lastItem = allItems[allItems.length-1]