In-database sharded queue

One or more non-transitory computer-readable media storing one or more sequences of instructions which, when executed by one or more processors, cause:

• storing messages from a plurality of enqueuers of a particular queue in a plurality of shards of the particular queue;
• wherein, within each shard, messages are ordered relative to all other messages in the shard based on their respective enqueue times;
• wherein the particular queue is implemented using a queue table maintained by a relational database system;
• wherein each shard of the plurality of shards is assigned one or more rows of the queue table maintained by the relational database system;
• wherein the plurality of enqueuers includes a first enqueuer and a second enqueuer;
• wherein storing messages from the plurality of enqueuers includes:
• storing all messages from the first enqueuer in first one or more rows of the queue table that are assigned to a first shard of the plurality of shards, and
• storing all messages from the second enqueuer in second one or more rows of the queue table that are assigned to a second shard of the plurality of shards,
• wherein the first one or more rows of the queue table are different from the second one or more rows of the queue table,
• wherein one or more messages from the first enqueuer and one or more messages from the second enqueuer are for a particular subscriber of the particular queue;
• dequeuing messages, from the particular queue, for the particular subscriber by dequeuing messages, for the particular subscriber, from both the first shard and the second shard.