[P4-dev] table questions

brian fiegen brianfiegen at gmail.com
Sun Jul 26 07:48:16 EDT 2015


I have a few questions about tables:

   - suppose one inserts a <key1, value1> into a table and then at some
   point in the future inserts a <key1, value2> into the table.  Does this
   operation result in both entries in the table?  Or the most recent one?  Or
   is the result of these operations unknown?
   - if one defines a table to be of size 50 and there are 50 elements in
   the table and 51st unique element is added to the table, what happens?Does
   an error get returned and the 51st element isn’t inserted?  Does one of the
   existing elements get randomly picked and removed to make room?
   - Does a default table action consume a spot in the table?
   - Is it possible to insert into a table a “value" which has variable
   length?   Basically I’m thinking of this “value” as being a sequence of
   bytes that are a header to be inserted into the packet.    What would be
   the mechanism to reference and process this variable length byte sequence
   on the action side?

Thanks
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