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From Alessandro Benedetti <abenede...@apache.org>
Subject Re: Is it safe to upgrade an existing field to docvalues?
Date Thu, 25 Aug 2016 10:49:26 GMT
> switching is done in Solr on field.hasDocValues. The code would be amended
> to (field.hasDocValues && field.useDocValues) throughout.
>

This is correct. Currently we use DocValues if they are available, and to
check the availabilty we check the schema attribute.
This can be problematic in the scenarios you described ( for example half
the index has docValues for a field and the other half not yet ).

Your proposal is interesting.
Technically it should work and should allow transparent migration from not
docValues to docValues.
But it is a risky one, because we are decreasing the readability a bit (
althought a user will specify the attribute only in special cases like
yours) .

The only problem I see is that the same discussion we had for docValues
actually applies to all other invasive schema changes :
1) you change the field type
2) you enable or disable term vectors
3) you enable/disable term positions,offsets ect ect

So basically this is actually a general problem, that probably would
require a general re-think .
So although  can be a quick fix that will work, I fear can open the road to
messy configuration attributes.

Cheers
-- 
--------------------------

Benedetti Alessandro
Visiting card : http://about.me/alessandro_benedetti

"Tyger, tyger burning bright
In the forests of the night,
What immortal hand or eye
Could frame thy fearful symmetry?"

William Blake - Songs of Experience -1794 England

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