Query processing with limit optimization in a database system

A query processing system includes:

• at least one processor;
• and
• a memory that stores operational instructions that, when executed by the at least one processor, cause the query processing system to perform operations that include:
• determining a query for execution that indicates a join expression and further indicates a threshold maximum number of output rows for the join expression;
• determining a query operator execution flow for the join expression that includes performance of two join operations based on the threshold maximum number of output rows for the join expression, wherein a union of output of the two join operations is semantically equivalent to an output of the join expression;
• and
• executing the query based on:
• performing the two join operations in parallel upon sets of input rows;
• and
• based on determining a set of output rows outputted by the two join operations has reached the threshold maximum number of output rows, finalizing execution of the query before at least one of the two join operations has finished processing its input rows.

A non-transitory computer readable storage medium comprises:

• at least one memory section that stores operational instructions that, when executed by at least one processing module that includes a processor and a memory, causes the at least one processing module to:
• determine a query for execution that indicates a join expression and further indicates a threshold maximum number of output rows for the join expression;
• determine a query operator execution flow for the join expression that includes performance of two join operations based on the threshold maximum number of output rows for the join expression, wherein a union of output of the two join operations is semantically equivalent to an output of the join expression;
• and
• execute the query based on:
• performing the two join operations in parallel upon sets of input rows;
• and
• based on determining a set of output rows outputted by the two join operations has reached the threshold maximum number of output rows, finalizing execution of the query before at least one of the two join operations has finished processing its input rows.