Oracle International Corporation

Devendra Singh

Shubha Bose

James William Stamos

Mukesh Jaiswal

Alan Robert Downing

Yang Seok Ki

Neerja Bhatt

Gaurav Garg

Anil Madan

Abhishek Saxena

Sunitha Subramanyam

Sujatha Janardhanan

Abhilash Tomar

Techniques are described herein for achieving physically dispersed item-dispersal patterns in queue tables that are used as circular buffers in a FIFO system. The techniques achieve the physically dispersed item-dispersal patterns while retaining FIFO semantics, efficient data ingest, efficient data access, and low latency for both fixed and variable-size ingest data. Because consecutively inserted rows are written to physically dispersed locations on persistent storage, lock contention between concurrent ingest sessions is significantly reduced. Once a physically dispersed item-dispersal pattern is established for a first set of inserted rows, subsequent rows are added by overwriting the existing rows. The physical dispersal of the initial rows may be accomplished by setting values in a slot number column such that updates that are made in a sequence that is based on the slot number column exhibit a desired physical dispersal pattern.

Avoiding hot spots during ingest where ingest ordering must be preserved

A DBMS maintains delayed and non-delayed messages within a non-delay shard and a delay shard that function as a pair. The DBMS stages non-delayed messages in enqueue-time order within the non-delay shard, and maintains a non-delay dequeue pointer that moves in physical order of the enqueued non-delay messages. The DBMS stages delayed messages in enqueue-time order within bucket shards of the delay shard. Each bucket shard, of a delay shard, represents a time span of delivery times, and messages are assigned thereto based on message delivery time. The delay dequeue pointer comprises a sub-routine to determine the message with the minimum delivery time within a current bucket shard with a time span that includes the current time. The DBMS delivers the next available message out of the delayed and non-delayed shards by comparing the delivery time of the next available message from each shard and delivering the earliest available message.

Messages with delayed delivery in an in-database sharded queue

A method and apparatus for message cache management for message queues is provided. A plurality of messages from a plurality of enqueuers are enqueued in a queue comprising one or more shards, each shard comprising one or more subshards. A message cache is maintained in memory. Enqueuing a message includes enqueuing the message in a current subshard of a particular shard, which includes storing the message in a cached subshard corresponding to the current subshard of the particular shard. For each dequeuer-shard pair, a dequeue rate is determined. Estimated access time data is generated that includes an earliest estimated access time for each of a plurality of subshards based on the dequeuer-shard pair dequeue rates. A set of subshards is determined for storing as cached subshards in the message cache based on the earliest estimated access times for the plurality of subshards.

Message cache management for message queues

A method and apparatus for an in-database sharded queue that supports JMS session ordering is provided. Messages from a plurality of enqueuers are stored in a plurality of shards of a particular queue. For each enqueuer, all messages are stored in only one of the shards. Each shard includes one or more subshards, each subshard having one or more partitions of a queue table maintained by a relational database system. All messages from a first enqueuer are stored in partitions of the queue table that are assigned to a first shard of the plurality of shards. All messages from a second enqueuer are stored in partitions of the queue table that are assigned to a second shard of the plurality of shards. Subscribers of the particular queue are caused to dequeue messages from the plurality of shards.

In-database sharded queue

Handling memory pressure in an in-database sharded queue is described. Messages from a plurality of enqueuers are stored in a plurality of shards of a sharded queue. Messages from a first enqueuer are stored in a first shard. A queue table corresponding to the sharded queue is maintained. In volatile memory, a plurality of message caches is maintained, each message cache corresponding to a shard of the plurality of shards. Memory pressure is detected based on memory usage of the volatile memory. To store a specific message from the enqueuer, the specific message is stored in rows of the queue table that are assigned to the first shard. When memory pressure is not detected, the specific message is stored in a first message cache corresponding to the first shard. Subscribers of the sharded queue are caused to dequeue messages from the plurality of shards.

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Bengaluru, India

Devendra Singh