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What are the consequences of adding a column to an exiting HIVE table ?

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Suppose that a couple hundred Gigs after starting to use HIVE I want to add a column. From the various articles & pages I have seen, I cannot understand the consequences in terms of

  • storage space required (double ?)
  • blocking (can I still read the table in other processes) ?
  • time (is it quick or as slow as a MysqL change ?)
  • underlying storage (do I need to change all the underlying files ? How can it be done using RCFile ?)

Bonus to whoever can answer the same question on structs in a HIVE column.

table schema hadoop change hive
asked February 21, 2011 6:15 am CST
bitbox
posted via StackOverflow

1 Answers

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If you add a column to a hive table, only the underlying metastore is updated.

  • The required storage space is not increased as long as you do not add data
  • The change can be made while other processes are accessing the table
  • The change is very quick (only the underlying metastore is updated)
  • You do not have to change the underlying files. Existing records have the value null for the new column

I hope this helps.

answered February 23, 2011 2:21 am CST
altus-insight

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