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When using Redis in order to create a "record" you can create a hash with several fields. For example:
HMSET myhash field1 "Hello" field2 "World"
HMSET myhash2 field1 "Goodbye" field2 "World"
You can retrieve this by knowing the key values, however what I want to know is there any way to retrieve all hashes that have "World" in field2?
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Redis HSET command is used to set field in the hash stored at the key to value. If the key does not exist, a new key holding a hash is created. If the field already exists in the hash, it is overwritten.
A Redis hash is a data type that represents a mapping between a string field and a string value. Hashes can hold many field-value pairs and are designed to not take up much space, making them ideal for representing data objects.
It is implemented as a Hash table and handles collisions by Chaining. A Redis Hash can store up to 4 billion key value pairs. If the value is Integer, Redis hash allows you to atomically increment or decrement the value.
NO, Redis hash doesn't maintain the order. Since it's a hash, it's unordered.
There are no indexes in redis, and it doesn't implement SQL. It's a key-value store. You provide a key, it gets you a value.
That said, you can implement this by maintaining secondary indexes yourself. For example:
create a record and an index entry
HMSET myhash field1 Hello field2 World
SADD field2_world myhash
update a record, delete old index entry, create new one
SREM field2_world myhash
HMSET myhash field2 Mundo
SADD field2_mundo myhash
find all records which have "World" in field2
SMEMBERS field2_world
I hope you get the idea.
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