Looking for a best practice to get all data according to some filters

Hi,

I was wondering about best practices to to get all data according to some
filters.
The options as I see them are:

  • Use a very big size that will return all accounts, i.e. use some value
    like 1m to make sure I get everything back (even if I need just a few
    hundreds or tens of documents). This is the quickest way, development wise.
  • Use paging - using size and from. This requires looping over the
    result and the performance gets worse as we advance to later pages. Also,
    we need to use preference if we want to get consistent results over the
    pages. Also, it's not clear what's the recommended size for each page.
  • Use scan/scroll - this gives consistent paging but also has several
    drawbacks: If I use search_type=scan then it can't be sorted; using
    scan/scroll is (maybe) less performant than paging (the documentation says
    it's not for realtime use); again not clear which size is recommended.

So you see - many options and not clear which path to take.

What do you think?

Thanks,
Ron

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Scan/scroll is the best option to extract a huge amount of data.
Never use size:10000000 or from:10000000.

It's not realtime because you basically scroll over a given set of segments and all new changes that will come in new segments won't be taken into account during the scroll.
Which is good because you won't get inconsistent results.

About size, I'd would try and test. It depends on your docs size I believe.
Try with 10000 and see how it goes when you increase it. You will may be discover that getting 1010000 docs is the same as 1100000. :slight_smile:

Best

David

Le 10 déc. 2014 à 19:09, Ron Sher ron.sher@gmail.com a écrit :

Hi,

I was wondering about best practices to to get all data according to some filters.
The options as I see them are:
Use a very big size that will return all accounts, i.e. use some value like 1m to make sure I get everything back (even if I need just a few hundreds or tens of documents). This is the quickest way, development wise.
Use paging - using size and from. This requires looping over the result and the performance gets worse as we advance to later pages. Also, we need to use preference if we want to get consistent results over the pages. Also, it's not clear what's the recommended size for each page.
Use scan/scroll - this gives consistent paging but also has several drawbacks: If I use search_type=scan then it can't be sorted; using scan/scroll is (maybe) less performant than paging (the documentation says it's not for realtime use); again not clear which size is recommended.
So you see - many options and not clear which path to take.

What do you think?

Thanks,
Ron

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So you're saying there's no impact on elasticsearch if I issue a large
size?
If that's the case then why shouldn't I just call size of 1M if I want to
make sure I get everything?

On Wednesday, December 10, 2014 8:22:47 PM UTC+2, David Pilato wrote:

Scan/scroll is the best option to extract a huge amount of data.
Never use size:10000000 or from:10000000.

It's not realtime because you basically scroll over a given set of
segments and all new changes that will come in new segments won't be taken
into account during the scroll.
Which is good because you won't get inconsistent results.

About size, I'd would try and test. It depends on your docs size I believe.
Try with 10000 and see how it goes when you increase it. You will may be
discover that getting 1010000 docs is the same as 1100000. :slight_smile:

Best

David

Le 10 déc. 2014 à 19:09, Ron Sher <ron....@gmail.com <javascript:>> a
écrit :

Hi,

I was wondering about best practices to to get all data according to some
filters.
The options as I see them are:

  • Use a very big size that will return all accounts, i.e. use some
    value like 1m to make sure I get everything back (even if I need just a few
    hundreds or tens of documents). This is the quickest way, development wise.
  • Use paging - using size and from. This requires looping over the
    result and the performance gets worse as we advance to later pages. Also,
    we need to use preference if we want to get consistent results over the
    pages. Also, it's not clear what's the recommended size for each page.
  • Use scan/scroll - this gives consistent paging but also has several
    drawbacks: If I use search_type=scan then it can't be sorted; using
    scan/scroll is (maybe) less performant than paging (the documentation says
    it's not for realtime use); again not clear which size is recommended.

So you see - many options and not clear which path to take.

What do you think?

Thanks,
Ron

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No I did not say that. Or I did not mean that. Sorry if it was unclear.
I said: don’t use large sizes:

Never use size:10000000 or from:10000000.

You should read this: http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-request-scroll.html#scroll-scan http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-request-scroll.html#scroll-scan

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Le 10 déc. 2014 à 21:16, Ron Sher ron.sher@gmail.com a écrit :

So you're saying there's no impact on elasticsearch if I issue a large size?
If that's the case then why shouldn't I just call size of 1M if I want to make sure I get everything?

On Wednesday, December 10, 2014 8:22:47 PM UTC+2, David Pilato wrote:
Scan/scroll is the best option to extract a huge amount of data.
Never use size:10000000 or from:10000000.

It's not realtime because you basically scroll over a given set of segments and all new changes that will come in new segments won't be taken into account during the scroll.
Which is good because you won't get inconsistent results.

About size, I'd would try and test. It depends on your docs size I believe.
Try with 10000 and see how it goes when you increase it. You will may be discover that getting 1010000 docs is the same as 1100000. :slight_smile:

Best

David

Le 10 déc. 2014 à 19:09, Ron Sher <ron....@gmail.com <javascript:>> a écrit :

Hi,

I was wondering about best practices to to get all data according to some filters.
The options as I see them are:
Use a very big size that will return all accounts, i.e. use some value like 1m to make sure I get everything back (even if I need just a few hundreds or tens of documents). This is the quickest way, development wise.
Use paging - using size and from. This requires looping over the result and the performance gets worse as we advance to later pages. Also, we need to use preference if we want to get consistent results over the pages. Also, it's not clear what's the recommended size for each page.
Use scan/scroll - this gives consistent paging but also has several drawbacks: If I use search_type=scan then it can't be sorted; using scan/scroll is (maybe) less performant than paging (the documentation says it's not for realtime use); again not clear which size is recommended.
So you see - many options and not clear which path to take.

What do you think?

Thanks,
Ron

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Just tested this.
When I used a large number to get all of my documents according to some
criteria (4926 in the result) I got:
13.951s when using a size of 1M
43.6s when using scan/scroll (with a size of 100)

Looks like I should be using the not recommended paging.
Can I make the scroll better?

Thanks,
Ron

On Wednesday, December 10, 2014 10:53:50 PM UTC+2, David Pilato wrote:

No I did not say that. Or I did not mean that. Sorry if it was unclear.
I said: don’t use large sizes:

Never use size:10000000 or from:10000000.

You should read this:
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-request-scroll.html#scroll-scan

--
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http://Elasticsearch.com

@dadoonet https://twitter.com/dadoonet | @elasticsearchfr
https://twitter.com/elasticsearchfr | @scrutmydocs
https://twitter.com/scrutmydocs

Le 10 déc. 2014 à 21:16, Ron Sher <ron....@gmail.com <javascript:>> a
écrit :

So you're saying there's no impact on elasticsearch if I issue a large
size?
If that's the case then why shouldn't I just call size of 1M if I want to
make sure I get everything?

On Wednesday, December 10, 2014 8:22:47 PM UTC+2, David Pilato wrote:

Scan/scroll is the best option to extract a huge amount of data.
Never use size:10000000 or from:10000000.

It's not realtime because you basically scroll over a given set of
segments and all new changes that will come in new segments won't be taken
into account during the scroll.
Which is good because you won't get inconsistent results.

About size, I'd would try and test. It depends on your docs size I
believe.
Try with 10000 and see how it goes when you increase it. You will may be
discover that getting 1010000 docs is the same as 1100000. :slight_smile:

Best

David

Le 10 déc. 2014 à 19:09, Ron Sher ron....@gmail.com a écrit :

Hi,

I was wondering about best practices to to get all data according to some
filters.
The options as I see them are:

  • Use a very big size that will return all accounts, i.e. use some
    value like 1m to make sure I get everything back (even if I need just a few
    hundreds or tens of documents). This is the quickest way, development wise.
  • Use paging - using size and from. This requires looping over the
    result and the performance gets worse as we advance to later pages. Also,
    we need to use preference if we want to get consistent results over the
    pages. Also, it's not clear what's the recommended size for each page.
  • Use scan/scroll - this gives consistent paging but also has several
    drawbacks: If I use search_type=scan then it can't be sorted; using
    scan/scroll is (maybe) less performant than paging (the documentation says
    it's not for realtime use); again not clear which size is recommended.

So you see - many options and not clear which path to take.

What do you think?

Thanks,
Ron

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Hi,
I am facing the same situation:
We would like to get all the ids of the documents matching certain
criteria. In the worst case (which is the one I am exposing here), the
documents matching the criteria would be around 200K, and in our first
tests it is really slow (around 15 seconds). However, if we do the same
query just for count documents, ES replies in just 10-15ms, which is
amazing.
I suspect that the problem is on the transport layer and the latency
generated by transferring a big JSON result.

Would you recommend, in a situation like this, to use another transport
layer like Thirf or a custom solution?.

Thanks in advance

El jueves, 11 de diciembre de 2014 14:00:05 UTC+1, Ron Sher escribió:

Just tested this.
When I used a large number to get all of my documents according to some
criteria (4926 in the result) I got:
13.951s when using a size of 1M
43.6s when using scan/scroll (with a size of 100)

Looks like I should be using the not recommended paging.
Can I make the scroll better?

Thanks,
Ron

On Wednesday, December 10, 2014 10:53:50 PM UTC+2, David Pilato wrote:

No I did not say that. Or I did not mean that. Sorry if it was unclear.
I said: don’t use large sizes:

Never use size:10000000 or from:10000000.

You should read this:
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-request-scroll.html#scroll-scan

--
David Pilato | Technical Advocate | Elasticsearch.com
http://Elasticsearch.com

@dadoonet https://twitter.com/dadoonet | @elasticsearchfr
https://twitter.com/elasticsearchfr | @scrutmydocs
https://twitter.com/scrutmydocs

Le 10 déc. 2014 à 21:16, Ron Sher ron....@gmail.com a écrit :

So you're saying there's no impact on elasticsearch if I issue a large
size?
If that's the case then why shouldn't I just call size of 1M if I want to
make sure I get everything?

On Wednesday, December 10, 2014 8:22:47 PM UTC+2, David Pilato wrote:

Scan/scroll is the best option to extract a huge amount of data.
Never use size:10000000 or from:10000000.

It's not realtime because you basically scroll over a given set of
segments and all new changes that will come in new segments won't be taken
into account during the scroll.
Which is good because you won't get inconsistent results.

About size, I'd would try and test. It depends on your docs size I
believe.
Try with 10000 and see how it goes when you increase it. You will may be
discover that getting 1010000 docs is the same as 1100000. :slight_smile:

Best

David

Le 10 déc. 2014 à 19:09, Ron Sher ron....@gmail.com a écrit :

Hi,

I was wondering about best practices to to get all data according to
some filters.
The options as I see them are:

  • Use a very big size that will return all accounts, i.e. use some
    value like 1m to make sure I get everything back (even if I need just a few
    hundreds or tens of documents). This is the quickest way, development wise.
  • Use paging - using size and from. This requires looping over the
    result and the performance gets worse as we advance to later pages. Also,
    we need to use preference if we want to get consistent results over the
    pages. Also, it's not clear what's the recommended size for each page.
  • Use scan/scroll - this gives consistent paging but also has
    several drawbacks: If I use search_type=scan then it can't be sorted; using
    scan/scroll is (maybe) less performant than paging (the documentation says
    it's not for realtime use); again not clear which size is recommended.

So you see - many options and not clear which path to take.

What do you think?

Thanks,
Ron

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Again, why not use a very large count size? What are the implications of
using a very large count?
Regarding performance - it seems doing 1 request with a very large count
performs better than using scan scroll (with count of 100 using 32 shards)

On Wednesday, December 10, 2014 10:53:50 PM UTC+2, David Pilato wrote:

No I did not say that. Or I did not mean that. Sorry if it was unclear.
I said: don’t use large sizes:

Never use size:10000000 or from:10000000.

You should read this:
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-request-scroll.html#scroll-scan

--
David Pilato | Technical Advocate | Elasticsearch.com
http://Elasticsearch.com

@dadoonet https://twitter.com/dadoonet | @elasticsearchfr
https://twitter.com/elasticsearchfr | @scrutmydocs
https://twitter.com/scrutmydocs

Le 10 déc. 2014 à 21:16, Ron Sher <ron....@gmail.com <javascript:>> a
écrit :

So you're saying there's no impact on elasticsearch if I issue a large
size?
If that's the case then why shouldn't I just call size of 1M if I want to
make sure I get everything?

On Wednesday, December 10, 2014 8:22:47 PM UTC+2, David Pilato wrote:

Scan/scroll is the best option to extract a huge amount of data.
Never use size:10000000 or from:10000000.

It's not realtime because you basically scroll over a given set of
segments and all new changes that will come in new segments won't be taken
into account during the scroll.
Which is good because you won't get inconsistent results.

About size, I'd would try and test. It depends on your docs size I
believe.
Try with 10000 and see how it goes when you increase it. You will may be
discover that getting 1010000 docs is the same as 1100000. :slight_smile:

Best

David

Le 10 déc. 2014 à 19:09, Ron Sher ron....@gmail.com a écrit :

Hi,

I was wondering about best practices to to get all data according to some
filters.
The options as I see them are:

  • Use a very big size that will return all accounts, i.e. use some
    value like 1m to make sure I get everything back (even if I need just a few
    hundreds or tens of documents). This is the quickest way, development wise.
  • Use paging - using size and from. This requires looping over the
    result and the performance gets worse as we advance to later pages. Also,
    we need to use preference if we want to get consistent results over the
    pages. Also, it's not clear what's the recommended size for each page.
  • Use scan/scroll - this gives consistent paging but also has several
    drawbacks: If I use search_type=scan then it can't be sorted; using
    scan/scroll is (maybe) less performant than paging (the documentation says
    it's not for realtime use); again not clear which size is recommended.

So you see - many options and not clear which path to take.

What do you think?

Thanks,
Ron

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Implication is the memory needed to be allocated on each shard.

David

Le 14 déc. 2014 à 05:46, Ron Sher ron.sher@gmail.com a écrit :

Again, why not use a very large count size? What are the implications of using a very large count?
Regarding performance - it seems doing 1 request with a very large count performs better than using scan scroll (with count of 100 using 32 shards)

On Wednesday, December 10, 2014 10:53:50 PM UTC+2, David Pilato wrote:
No I did not say that. Or I did not mean that. Sorry if it was unclear.
I said: don’t use large sizes:

Never use size:10000000 or from:10000000.

You should read this: http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-request-scroll.html#scroll-scan

--
David Pilato | Technical Advocate | Elasticsearch.com
@dadoonet | @elasticsearchfr | @scrutmydocs

Le 10 déc. 2014 à 21:16, Ron Sher ron....@gmail.com a écrit :

So you're saying there's no impact on elasticsearch if I issue a large size?
If that's the case then why shouldn't I just call size of 1M if I want to make sure I get everything?

On Wednesday, December 10, 2014 8:22:47 PM UTC+2, David Pilato wrote:
Scan/scroll is the best option to extract a huge amount of data.
Never use size:10000000 or from:10000000.

It's not realtime because you basically scroll over a given set of segments and all new changes that will come in new segments won't be taken into account during the scroll.
Which is good because you won't get inconsistent results.

About size, I'd would try and test. It depends on your docs size I believe.
Try with 10000 and see how it goes when you increase it. You will may be discover that getting 1010000 docs is the same as 1100000. :slight_smile:

Best

David

Le 10 déc. 2014 à 19:09, Ron Sher ron....@gmail.com a écrit :

Hi,

I was wondering about best practices to to get all data according to some filters.
The options as I see them are:
Use a very big size that will return all accounts, i.e. use some value like 1m to make sure I get everything back (even if I need just a few hundreds or tens of documents). This is the quickest way, development wise.
Use paging - using size and from. This requires looping over the result and the performance gets worse as we advance to later pages. Also, we need to use preference if we want to get consistent results over the pages. Also, it's not clear what's the recommended size for each page.
Use scan/scroll - this gives consistent paging but also has several drawbacks: If I use search_type=scan then it can't be sorted; using scan/scroll is (maybe) less performant than paging (the documentation says it's not for realtime use); again not clear which size is recommended.
So you see - many options and not clear which path to take.

What do you think?

Thanks,
Ron

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Search consumes O(offset + size) memory and O(ln(offset +
size)*(offset+size) CPU. Scan scroll has higher overhead but is O(size) the
whole time. I don't know the break even point.

The other thing is that scroll provides a consistent snapshot. That means
it consumes resources you shouldn't let end users expose but it won't miss
results or have repeats like scrolling with increasing offset.

You can certainly do large fetches with big size but its less stable in
general.

Finally, scan/scroll has always been pretty quick for me. I usually use a
batch size in the thousands.

Nik
On Dec 14, 2014 4:13 AM, "David Pilato" david@pilato.fr wrote:

Implication is the memory needed to be allocated on each shard.

David

Le 14 déc. 2014 à 05:46, Ron Sher ron.sher@gmail.com a écrit :

Again, why not use a very large count size? What are the implications of
using a very large count?
Regarding performance - it seems doing 1 request with a very large count
performs better than using scan scroll (with count of 100 using 32 shards)

On Wednesday, December 10, 2014 10:53:50 PM UTC+2, David Pilato wrote:

No I did not say that. Or I did not mean that. Sorry if it was unclear.
I said: don’t use large sizes:

Never use size:10000000 or from:10000000.

You should read this: http://www.elasticsearch.org/guide/en/
elasticsearch/reference/current/search-request-scroll.html#scroll-scan

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Le 10 déc. 2014 à 21:16, Ron Sher ron....@gmail.com a écrit :

So you're saying there's no impact on elasticsearch if I issue a large
size?
If that's the case then why shouldn't I just call size of 1M if I want to
make sure I get everything?

On Wednesday, December 10, 2014 8:22:47 PM UTC+2, David Pilato wrote:

Scan/scroll is the best option to extract a huge amount of data.
Never use size:10000000 or from:10000000.

It's not realtime because you basically scroll over a given set of
segments and all new changes that will come in new segments won't be taken
into account during the scroll.
Which is good because you won't get inconsistent results.

About size, I'd would try and test. It depends on your docs size I
believe.
Try with 10000 and see how it goes when you increase it. You will may be
discover that getting 1010000 docs is the same as 1100000. :slight_smile:

Best

David

Le 10 déc. 2014 à 19:09, Ron Sher ron....@gmail.com a écrit :

Hi,

I was wondering about best practices to to get all data according to
some filters.
The options as I see them are:

  • Use a very big size that will return all accounts, i.e. use some
    value like 1m to make sure I get everything back (even if I need just a few
    hundreds or tens of documents). This is the quickest way, development wise.
  • Use paging - using size and from. This requires looping over the
    result and the performance gets worse as we advance to later pages. Also,
    we need to use preference if we want to get consistent results over the
    pages. Also, it's not clear what's the recommended size for each page.
  • Use scan/scroll - this gives consistent paging but also has
    several drawbacks: If I use search_type=scan then it can't be sorted; using
    scan/scroll is (maybe) less performant than paging (the documentation says
    it's not for realtime use); again not clear which size is recommended.

So you see - many options and not clear which path to take.

What do you think?

Thanks,
Ron

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Just to reword what others have said, ES will allocate memory for [size] scores as I understand it (per shard?) regardless of the final result count. If you're getting back 4986 results from a query, it'd be faster to use "size": 4986 than "size": 1000000.

What I've done in similar situations is to issue a count first with the same filter (which is very fast), then use the result of that in the size field. It worked much better/faster than using a default large size.

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