Question about SQL query when persistence enabled

[Justin Ji <bi...@foxmail.com>]

According to the document, we know that there is only a subset of data in
memory while the full data set in the disk when persistence enabled. I have
some questions with regards to this point:

Let's say I have a SQL like:
select * from city where provinceId = '1';
1. If some data is in memory while others in the disk,  would ignite query
data from disk? After the query, would those data in the disk be loaded to
the memory?
2. If all data is in the memory, would ignite query data from disk? Or only
query from disk?
3. If all data is in the disk, would ignite query from memory?

4. Is there a document can explain the mechanism in detail?

Looking forward to your reply!




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Sent from: http://apache-ignite-users.70518.x6.nabble.com/

Re: Question about SQL query when persistence enabled

[Denis Mekhanikov <dm...@gmail.com>]

Justin,

You can think of your dataset as if there was no separation between disk
and memory. So, all data is always available for all SQL operations.

Data, which is available in memory will be used right away. Data, which is
present on disk only will be loaded into memory first, and after that used
by the query.

You can read about page rotation here:
https://cwiki.apache.org/confluence/display/IGNITE/Ignite+Durable+Memory+-+under+the+hood
But I'm not sure, that you really need such details to understand the
principles of this mechanism.

Denis

пн, 25 мар. 2019 г. в 10:19, Justin Ji <bi...@foxmail.com>:

> According to the document, we know that there is only a subset of data in
> memory while the full data set in the disk when persistence enabled. I have
> some questions with regards to this point:
>
> Let's say I have a SQL like:
> select * from city where provinceId = '1';
> 1. If some data is in memory while others in the disk,  would ignite query
> data from disk? After the query, would those data in the disk be loaded to
> the memory?
> 2. If all data is in the memory, would ignite query data from disk? Or only
> query from disk?
> 3. If all data is in the disk, would ignite query from memory?
>
> 4. Is there a document can explain the mechanism in detail?
>
> Looking forward to your reply!
>
>
>
>
> --
> Sent from: http://apache-ignite-users.70518.x6.nabble.com/
>