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This is just wrong. The smaller file needs to fit in memory as an array (hash table) to overcome the ordering problem. The larger file is processed serially, record by record. In extreme conditions, it would be a trivial improvement to split the smaller file into, say 1GB sections, and make multiple passes over the larger file. The first pass might need to be "special" to restructure the input columns to the "joined" format, and place default values in columns where the first pass did not contain the required update data.

Paul_Pedant
– Paul_Pedant

2020-02-08 13:58:26 +00:00
Commented Feb 8, 2020 at 13:58

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