range example please

[cekvenich2]

Hi, I'm trying to use range to 'scan' rows.

I'm confused by start/end args. Is there a real example?
It is not same as offset.

tia for past support.

[kriszyp]

There are quite a few examples of range arguments in the tests, like https://github.com/DoctorEvidence/lmdb-js/blob/master/test/index.test.js#L396, although not sure if there is something more real or specific you are looking for. The start and end properties specify the key range, and then within that range, the offset specifies the number of entries to skip before returning/iterating entries, and the limit specifies the maximum number of entries to return/iterate through. Are you looking for a specific use case?

[cekvenich2]

I'm looking for hello world. Is 1 and 100 good for start and end?

…

On Mon, Dec 6, 2021 at 7:13 PM Kris Zyp ***@***.***> wrote: There are quite a few examples of range arguments in the tests, like https://github.com/DoctorEvidence/lmdb-js/blob/master/test/index.test.js#L396, although not sure if there is something more real or specific you are looking for. The start and end properties specify the key range, and then within that range, the offset specifies the number of entries to skip before returning/iterating entries, and the limit specifies the maximum number of entries to return/iterate through. Are you looking for a specific use case? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#105 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ASK4M5DNJ7IERCEU6FBGAOLUPVNSZANCNFSM5JQANCGA> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[kriszyp]

Ok, here is a simple example:

let db = open('my-db');
for (let i = 0; i < 50; i++) {
  // adds 50 entries, with keys from 100 - 149
  await db.put(i + 100, 'value' + i);
}
for (let { key, value } of getRange({ start: 120, end: 130 }) {
  // this would iterate entries from 120 - 129
}
for (let { key, value } of getRange({ start: 200 }) {
  // there are no keys over 200, so this wouldn't find any entries
}
for (let { key, value } of getRange({ start: 100, end: 130, offset: 10 }) {
  // this would start at 100, skip 10 entries, and iterate entries 110 - 129
}

[cekvenich2]

@kriszyp THANK YOU.
So you assume some kind of a sequence # for key. If I used a random GUID, then one could not get range. There would be no way 'scan'.
Based on your example, and docs - that is my understanding now. Correct?

I could use db.getKeys to scan from start, and use limit and offset to get 1K rows at a time and continue.

[kriszyp]

Yes, that's correct, there wouldn't be anything meaningful about doing a range query on random GUIDs. But, like you said, you could still do range query of the whole database, and use offset/limit to get sections (and you could do that by just omitting the start and end properties, and then the range will be across the whole database):

let iterable = db.getRange({
  offset: 2000, // start at row 2000
  limit: 1000, // iterate through a thousand
})

[cekvenich2]

Got it thanks.