Storing data items and identifying stored data items

A method of storing a data item, the method comprising:

• receiving, in computer memory, a data item to be stored;
• writing the data item to a data chunk of a stream segment, said stream segment including a stream segment header and a plurality of data chunks;
• obtaining a first identifier from the data item;
• writing the first identifier of the data item to the stream segment header of the stream segment to which the data item is written;
• obtaining a second identifier from the data item, the second identifier being different from the first identifier;
• and
• writing the second identifier of the data item to a header of the data chunk of the stream segment to which the data item is written;
• whereby the first identifier in the stream segment header can be used to identify if any data items in any of the data chunks of the stream segments include the first identifier, and whereby the second identifier in the header of the data chunk of the stream segment can be used to identify if any data items in the data chunk include the second identifier.

A non-transitory computer-readable storage medium comprising a set of computer-readable instructions stored thereon, which, when executed by a computer system, cause the computer system to carry out a method of identifying a data item stored in the computer system based on a query identifier of the data item, the method comprising:

• querying a stream segment header of a stream segment with a query identifier, wherein the stream segment comprises a stream segment header and one or more data chunks, wherein each data chunk comprises data items and the stream segment header comprises identifiers of the data items in the data chunks, wherein the querying of the stream segment header identifies if any of the data items in the data chunks of the stream segment have said query identifier;
• if any of the data items in the data chunks of the stream segment have said query identifier, querying said data chunks of the stream segment with said query identifier to identify which data chunks of the stream segment have said query identifier;
• and
• at least one of:
• retrieving at least one of the data items in at least one of the data chunks of the stream segment that has said query identifier;
• and deleting at least one of the data items in at least one of the data chunks of the stream segment that has said query identifier.