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Update VTGateV3Features.md
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#### Hashed sharding key
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#### Hashed sharding key
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If the application's sharding key is a monotonically increasing number, then you may not get well-balanced shards. In such cases, you can ask V3 to route queries based on the hash of the main sharding key.
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If the application's sharding key is a monotonically increasing number, then you may not get well-balanced shards. In such cases, you can ask V3 to route queries based on the hash of the main sharding key.
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Vitess's filtered replication currently requires that the hash value be physically present as a column in each table. To satisfy this need, you still need to create a column to store this hash value. However, V3 will take care of populating this on your behalf. *We will soon be removing this restriction once we change filtered replication to also perform the same hashing.*
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Vitess's filtered replication currently requires that the hash value be physically present as a column in each table. To satisfy this need, you still need to create a column to store this hash value. However, V3 will take care of populating this on your behalf.
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*We will soon be removing this restriction once we change filtered replication to also perform the same hashing.*
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#### Auto-increment columns
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#### Auto-increment columns
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When a table gets sharded, you are no longer able to use MySQL's auto increment functionality. V3 allows you to designate a table in an unsharded database as the source of auto-increment ids. Once you've specified this, V3 will transparently use generated values from this table to keep the auto-increment going. The auto-increment can column can in turn be a basic or hashed sharding key. If it's a hashed sharding key, the newly generated value will be hashed before the query is routed.
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When a table gets sharded, you are no longer able to use MySQL's auto increment functionality. V3 allows you to designate a table in an unsharded database as the source of auto-increment ids. Once you've specified this, V3 will transparently use generated values from this table to keep the auto-increment going. The auto-increment can column can in turn be a basic or hashed sharding key. If it's a hashed sharding key, the newly generated value will be hashed before the query is routed.
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