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Can constants in messages be changed without troubles with respect to "old" data?

asked 2014-07-10 02:37:21 -0500

Wolf gravatar image

Hi guys,

If I change (or add/remove) fields in message files "old" messages, e. g. record in bags, can no longer be subscribed by the node using the new message description, because md5sum and stuff do no longer fit...

Now my question: What happens if I add/remove/modify constant definitions ( http://wiki.ros.org/msg#Constants ) in messages? Will I still be able to use bags I recorded prior to the changes?

Thanks in advance, Wolf

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answered 2014-07-10 14:19:08 -0500

tfoote gravatar image

You can add constants. If you remove or modify constants you will corrupt the data since the constant values are stored as the values.

Any of these will cause an MD5sum change and will require running a bag migration script to update the md5sum but it will not actually change the payload.

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Asked: 2014-07-10 02:37:21 -0500

Seen: 241 times

Last updated: Jul 10 '14