Efficient opcode-driven pipelined execution of multi-level hash joins

Abstract

An efficient join processing technique is provided that improves multi-level hash join performance by decomposing join operations into a set of opcodes that describe any complex hash join, pipelining execution of these opcodes across join levels, and sharing join operand metadata across opcodes. Complex multi-level joins are easier to describe and execute when decomposed into opcodes. The join technique decomposes multi-level join operations into a minimal set of opcodes such that the join work at each node of the multi-level join can be fully described as an execution of a sequence of opcodes. Operand metadata is shared across the opcodes of all join levels that reference the operand, thereby obviating the need to copy or transmit rows between the join nodes.