Abstract: Computer-readable media, methods, and systems are disclosed for utilizing partition-based locking mechanisms to improve execution of overlapping data definition language (DDL) and data manipulation language (DML) operations on a partitioned database table. A first node receives a DML statement associated with a first transaction. The first node acquires a intent exclusive lock on table metadata. A second node receives a DDL statement associated with a second transaction and acquires an exclusive metadata lock on the partitioned table metadata. Next, an intent exclusive lock is acquired for the relevant partition table data on the second node and an exclusive lock on table metadata on the second node. The second transaction waits for the DML operation of the first transaction to complete. Then the first transaction is committed. Finally exclusive locks are acquired on table data and metadata and the second transaction is executed and committed.

Abstract: Computer-readable media, methods, and systems are disclosed for database table partition pruning based on statistical information associated with non-partition columns. A tree partition specification is received defining partitions for a plurality of computed column statistics. Respective partitions are created for the plurality of computed column statistics based on the tree partition specification. A request is received to compute statistics for a plurality of columns of the plurality of computed column statistics to result in a plurality of computed column statistics. In response to determining that one or more modifications have been made to the partitioned database, the plurality of computed column statistics is marked as invalid. The computed column statistics are refreshed in response to modifications of the partitioned table. Thereafter, the statistics are marked as valid. Unnecessary table partitions are pruned based on the statistics, and the associated query is executed.

Abstract: A single-core optical transceiver is an optical transceiver for transmitting or receiving an optical signal through a single optical fiber. The single-core optical transceiver has a light emitting device for transmitting the optical signal and a light receiving device for receiving the optical signal. The light emitting device is an LED configured including a sapphire substrate arranged on a light receiving surface of the light receiving device so as to be coaxial with the light receiving surface, and a nitride semiconductor layer laid on the sapphire substrate. Even with the light emitting device being arranged on the light receiving surface of the light receiving device, the optical signal from the optical fiber can be received on the entire area of the light receiving surface, so as to adequately improve the light sensitivity.

Abstract: A single-core optical transceiver is an optical transceiver for transmitting or receiving an optical signal through a single optical fiber. The single-core optical transceiver has a light emitting device for transmitting the optical signal and a light receiving device for receiving the optical signal. The light emitting device is an LED configured including a sapphire substrate arranged on a light receiving surface of the light receiving device so as to be coaxial with the light receiving surface, and a nitride semiconductor layer laid on the sapphire substrate. Even with the light emitting device being arranged on the light receiving surface of the light receiving device, the optical signal from the optical fiber can be received on the entire area of the light receiving surface, so as to adequately improve the light sensitivity.