[DOCS-10112] Choosing a shard key should explain how only the first field in a compound shard key is used to select the shard for the data Created: 12/Apr/17 Updated: 30/Oct/23 |
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| Status: | Closed |
| Project: | Documentation |
| Component/s: | manual |
| Affects Version/s: | None |
| Fix Version/s: | Server_Docs_20231030 |
| Type: | Improvement | Priority: | Major - P3 |
| Reporter: | James Reitz | Assignee: | Unassigned |
| Resolution: | Won't Do | Votes: | 2 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Participants: | |
| Days since reply: | 1 year, 14 weeks, 2 days ago |
| Epic Link: | DOCSP-1769 |
| Description |
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The documentation here https://docs.mongodb.com/manual/core/sharding-shard-key/#choosing-a-shard-key doesn't mention that when using a compound shard key, only the first field in the key is used to determine on what shard the data resides. Other fields are used to help improve cardinality, and spread data across chunks, but not across shards. Since shard keys are immutable, this turns out to be a very important fact. |
| Comments |
| Comment by Education Bot [ 31/Oct/22 ] |
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Hello! This ticket has been closed due to inactivity. If you believe this ticket is still important, please reopen it and leave a comment to explain why. Thank you! |
| Comment by James Reitz [ 25/Apr/17 ] |
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I'm now questioning if my understanding of how shard keys work to distribute documents across shards is accurate based on a recent experience where I saw two different chunks within a sharded collection with the same value for the first field in their shard key residing on different chunks. Regardless, it would be nice if the documentation described how range-based partitioning/sharding works. |