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We have not implemented them before because they require the raw elements to be kept. It is easy to see why in the following example: current_min = 3; insert(2) => current_min = 2 // can be done without state delete(2) => needs to look at the state to determine new min! The aggregator state was a very simple key-value structure. To accomodate for min/max, we will make it into a more complex table, where we can encode a more complex structure. The key insight is that we can use a primary key composed of: 1) storage_id 2) zset_id, 3) element The storage_id and zset_id are our previous key, except they are now exploded to support a larger range of storage_id. With more bits available in the storage_id, we can encode information about which column we are storing. For aggregations in multiple columns, we will need to keep a different list of values for min/max! The element is just the values of the columns. Because this is a primary key, the data will be sorted in the btree. We can then just do a prefix search in the first two components of the key and easily find the min/max when needed. This new format is also adequate for joins. Joins will just have a new storage_id which encodes two "columns" (left side, right side).