Package org.apache.solr.common.cloud

Class CompositeIdRouter

  • public class CompositeIdRouter
extends HashBasedRouter
    CompositeIdRouter partitions ids based on a SEPARATOR, hashes each partition and merges the hashes together to map the id to a slice. This allows bucketing of like groups of ids. Allows basic separation split between 32 bits as example given below, or using bitsSeparator can specify exact bits 
     Example inputs:
 user!uniqueid
 app!user!uniqueid
 user/4!uniqueid
 app/2!user/4!uniqueid
    Lets say you had a set of records you want to index together such as a contact in a database, using a prefix of contact!contactid would allow all contact ids to be bucketed together. 
     An Example:
 If the id "contact!0000000KISS is passed 😘
 Take "contact"" and hash it with murmurhash3_x86_32
 result: -541354036
 bits: 11011111101110111001011111001100

 Take 0000000KISS and hash it with murmurhash3_x86_32
 result: 2099700320
 bits: 01111101001001101110001001100000

 Now we take the bits and apply a mask, since this is 32 bits the mask is the first 16 bits or the last 16 bits
 So uppermask = 0xFFFF0000  11111111111111110000000000000000
 So we bitwise AND to get half the original hash and only the upper 16 bits for 00T
 11011111101110111001011111001100
 11111111111111110000000000000000
 ________________________________
 11011111101110110000000000000000

 lowermask = 0x0000FFFF 00000000000000001111111111111111
 So we bitwise AND and get the lower 16 bits of the original hash for 0000000KISS
 01111101001001101110001001100000
 00000000000000001111111111111111
 ________________________________
 00000000000000001110001001100000

 Now we combine the hashes with a bitwise OR
 11011111101110110000000000000000
 00000000000000001110001001100000
 ________________________________
 11011111101110111110001001100000

 11011111101110111110001001100000 is the hash we return, bucketing the suffixed by prefix type prefix!suffix