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Custom sharding function

A custom sharding function can be used to determine the bucket number - location in the cluster - and used further in the cluster operations. For this purpose you need:

  1. a hash function
    As an example, a default function from tarantool/vshard - crc32 with specific polynomial value. Java doesn't have crc32 out of the box with the ability to pass a polynomial value, so we'll implement our own: https://github.com/tarantool/cartridge-java/blob/ef61296e2bec0f1fca3483225315590d614ea64d/src/test/java/io/tarantool/driver/integration/Utils.java#L93-L106
  2. the number of buckets
    This number can be obtained from Tarantool via vshard.router.bucket_count function out of vshard module https://github.com/tarantool/cartridge-java/blob/ef61296e2bec0f1fca3483225315590d614ea64d/src/test/java/io/tarantool/driver/integration/Utils.java#L48-L56

Then we can determine bucket id by passing your key through hash function and get the remainder of the division by number of buckets: https://github.com/tarantool/cartridge-java/blob/ef61296e2bec0f1fca3483225315590d614ea64d/src/test/java/io/tarantool/driver/integration/Utils.java#L68-L83

After that we may apply it in operations: https://github.com/tarantool/cartridge-java/blob/ef61296e2bec0f1fca3483225315590d614ea64d/src/test/java/io/tarantool/driver/integration/proxy/options/ProxySpaceInsertOptionsIT.java#L142-L160