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That refers to the total length of the row. InnoDB has a limit of
65k and NDB is limited to 14k. <br>
<br>
A simple example would be the volumes table in Cinder where the row
length goes beyond 14k. So in the IF logic block, I change columns
types that are vastly oversized such as status and attach_status,
which by default are 255 chars. So to determine a more appropriate
size, I look through the Cinder code to find where the possible
options/states are for those columns. Then I cut it down to a more
reasonable size. I'm very careful when I cut the size of a string
column to ensure that all of the possible values can be contained.<br>
<br>
In cases where a column is extremely large for capturing the outputs
of a command, I will change the type to Text or TinyText depending
on the length required. A good example of this is in the agents
table of Neutron where there is a column for configurations that has
a string length of 4096 characters, which I change to Text. Text
blobs are stored differently and do not count against the row
length.<br>
<br>
I've also observed differences between Kilo, Mitaka, and tip where
even for InnoDB some of these tables are getting wider than can be
supported. So in the case of Cinder, some of the columns have been
shifted to separate tables to fit within 65k. I've seen the same
thing in Neutron. So I fully expect that some of the services that
have table bloat will have to cut the lengths or break the tables up
over time anyways. As that happens, it reduces the amount of work
for me, which is a good thing.<br>
<br>
The most complicated database schemas to patch up are cinder,
glance, neutron, and nova due to the size and complexity of their
tables. Those also have a lot of churn between releases where the
schema changes more often. Other services like keystone, heat, and
ironic are considerably easier to work with and have well laid out
tables that don't change much.<br>
<br>
Thanks,<br>
Octave<br>
<br>
<div class="moz-cite-prefix">On 2/2/2017 1:25 PM, Mike Bayer wrote:<br>
</div>
<blockquote
cite="mid:b69525f2-9f47-fc52-b576-380ffc627def@redhat.com"
type="cite">
<br>
<br>
On 02/02/2017 02:52 PM, Mike Bayer wrote:
<br>
<blockquote type="cite">
<br>
But more critically I noticed you referred to altering the names
of
<br>
columns to suit NDB. How will this be accomplished? Changing
a column
<br>
name in an openstack application is no longer trivial, because
online
<br>
upgrades must be supported for applications like Nova and
Neutron. A
<br>
column name can't just change to a new name, both columns have
to exist
<br>
and logic must be added to keep these columns synchronized.
<br>
<br>
</blockquote>
<br>
correction, the phrase was "Row character length limits 65k ->
14k" - does this refer to the total size of a row? I guess rows
that store JSON or tables like keystone tokens are what you had in
mind here, can you give specifics ?
<br>
<br>
<br>
<br>
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