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lookup join

Short Description

A lookup join iterate through values from the first (smaller) looking up that value in the second (larger) one

Detailed Description

Thelookup joins node iterate through values from the first (smaller) looking up that value in the second (larger) one. These joins are used where the driving table is much smaller than the one used for the lookups and the lookup column must be indexed. A partial index can be used, but only if it contains the subset of rows being looked up.

CockroachDB processes a lookup join as follows:

  • A row is read from the smaller table.
  • The larger table is then scanned for a matching rows which are output if found.

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