[h2] Re: What's the recommended way to migrate from H2 1.3.175 to 1.4.195

[Steve McLeod]

Hendrik, I've answered your question in detail on StackOverflow.


On Friday, 5 May 2017 17:29:02 UTC+2, hendrik wrote:
>
> Hey there,
>
> asked this on Stackoverflow 
> 
>  
> the other day, but I guess this may be the better place (unless you're keen 
> on SO reputation...).
>
> Now that H2 1.4 is out of beta, I'd like to migrate my old 1.3.175 
> database to 1.4.195.
>
> Background info:
>
>- In the docs, database upgrade 
> does 
>not mention 1.4 yet.
>- The roadmap  still 
>lists "Automatic migration from 1.3 databases to 1.4." as "planned change".
>- The current state 
> of MVStore 
>is still labeled as "experimental".
>
> So, what's the recommended way to migrate?
>
> Additional aspects/bonus questions:
>
> Should I enable MVStore or stick with PageStore (pros/cons)? Which one 
> delivers better performance (multithreading is not important for me), which 
> one better stability, especially resilience against OutOfMemoryErrors?
>
> Thanks for your help!
>
> -hendrik
>

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[h2] Re: What's the recommended way to migrate from H2 1.3.175 to 1.4.195

[Christian MICHON]

Regular backups in order to recover from data corruption. Always a good 
practice.

Useful as I had a production db 24/7 for almost 1 year (using 1.3.176) and 
Windows updates made the database crash a few times.

As for the txt done by the recover, I guess it's just a debug log of the 
recovery mechanism. I cannot confirm, I'm not part of the h2 dev team.

On Tuesday, May 9, 2017 at 10:42:50 AM UTC+2, hendrik wrote:
>
>
>
> On Monday, May 8, 2017 at 2:02:04 PM UTC+2, Christian MICHON wrote:
>>
>> Yes you can use the 1.4 jar to export the script. I've done this already. 
>>
>> I would advice to use the default settings per version. 1.3 uses page 
>> store, 1.4 the newer store. Do not tweak the defaults settings except the 
>> cache size. 
>>
>> Try to keep also regular backups using SCRIPT TO.
>>
>
> Well, backups are always a good idea... Do you recommend this for a 
> particular reason?
> Thing is, I'm using H2 as embedded database for my product. It's going to 
> be shipped to thousands of users...
>  
>
>> Good luck with your migration.
>>
>
> Thank you! 
>
> And while I have your attention:
>
> org.h2.tools.Recover produces two files: a sql file and a .mv.txt file.
>
> What is the .mv.txt file good for? I couldn't find any documentation.
>

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[h2] Re: What's the recommended way to migrate from H2 1.3.175 to 1.4.195

[hendrik]

On Monday, May 8, 2017 at 2:02:04 PM UTC+2, Christian MICHON wrote:
>
> Yes you can use the 1.4 jar to export the script. I've done this already. 
>
> I would advice to use the default settings per version. 1.3 uses page 
> store, 1.4 the newer store. Do not tweak the defaults settings except the 
> cache size. 
>
> Try to keep also regular backups using SCRIPT TO.
>

Well, backups are always a good idea... Do you recommend this for a 
particular reason?
Thing is, I'm using H2 as embedded database for my product. It's going to 
be shipped to thousands of users...
 

> Good luck with your migration.
>

Thank you! 

And while I have your attention:

org.h2.tools.Recover produces two files: a sql file and a .mv.txt file.

What is the .mv.txt file good for? I couldn't find any documentation.

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[h2] Re: What's the recommended way to migrate from H2 1.3.175 to 1.4.195

[Christian MICHON]

Hi

Yes you can use the 1.4 jar to export the script. I've done this already. 

I would advice to use the default settings per version. 1.3 uses page store, 
1.4 the newer store. Do not tweak the defaults settings except the cache size. 

Try to keep also regular backups using SCRIPT TO.

Good luck with your migration. 

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[h2] Re: What's the recommended way to migrate from H2 1.3.175 to 1.4.195

[hendrik]

Thanks, Christian.

Can I create the script dump with the 1.4.195 version using ;mv_store=false in 
the connection URL? Or do I *must* I use the 1.3 jar? I guess my question 
is, did the PageStore format change at all between 1.3 and 1.4?

I assume the new database will be MVStore-based, unless I specify 
otherwise. Right?
Is there some info about the pros/cons MVStore vs. PageStore?
Why is MVStore still labeled as "experimental", even though it's the 
default storage engine? Perhaps because that part of the MVStore docs 
simply hasn't been updated yet?

Cheers,

-hendrik

On Saturday, May 6, 2017 at 11:10:16 PM UTC+2, Christian MICHON wrote:
>
> Hi,
>
> As simple as possible.
>
> Use SCRIPT to export SQL. Use RUNSCRIPT into a freshly created db with 
> 1.4.195
>
> Christian 
>
>

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