Oracle Corporation
Bit vector gather row count calculation and handling in direct memory access engine

Abstract:

Techniques are described herein for efficient movement of data from a source memory to a destination memory. In an embodiment, in response to a particular memory location being pushed into a first register within a first register space, the first set of electronic circuits accesses a descriptor stored at the particular memory location. The descriptor indicates a width of a column of tabular data, a number of rows of tabular data, and one or more tabular data manipulation operations to perform on the column of tabular data. The descriptor also indicates a source memory location for accessing the tabular data and a destination memory location for storing data manipulation result from performing the one or more data manipulation operations on the tabular data. Based on the descriptor, the first set of electronic circuits determines control information indicating that the one or more data manipulation operations are to be performed on the tabular data and transmits the control information, using a hardware data channel, to a second set of electronic circuits to perform the one or more operations. Based on the control information, the second set of electronic circuits retrieve the tabular data from source memory location and apply the one or more data manipulation operations to generate the data manipulation result. The second set of electronic circuits cause the data manipulation result to be stored at the destination memory location. Among the data manipulation operations that can be described are a bit vector based gather operation. The second set of electronic circuits determine a row count, which is generated efficiently by the second set of electronic circuits and is used to perform a gather operation and other types of data manipulation operations more efficiently.