Custom routing and multiple indexes where shard distribution is uniform

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1

I have an index a with a custom routing field (an int64).

I have a second index b, which is a pseudo-child of a. It shares the same custom routing value as a for "child" documents. In other words, without using a parent-child structure, I can use the routing value to find relevant documents in a and then search in b where b.a_id = a._id and b._routing = a._routing.

Both a and b have the same number of shards and these divide evenly into the number of nodes (let's say 32 shards each and 2 nodes).

My question is this: will ES put documents on the same node for a or b where the routing value is the same, or does it automatically offset the root (0) shard number per index?

2

Shards can be allocated or moved to any node so are not at all guaranteed to be collocates.

3

To reword my question, I'm more curious to know if ES will automatically assign hash(key) % node_count = 0 for all indexes by default to node 0 if all indexes have (shard_count % node_count) = 0.

4

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