Abstract: A query and response sub-system is operable to obtain a query and to generate an execution plan for a left inner join function of the query. The execution plan includes: identify left data of a column of the left table based on a reference column that is common to both tables; forward the rows of left data to memory allocated for a result table; identify right data of a column of the right table based on the reference column; temporarily store rows of the right data in memory allocated for the right table; identify rows of matching data from the rows of right data based on matching data of the reference column; add the rows of matching data to the result table; identify rows of non-matching data from the rows of right data based on data of the reference column; and add NULL to the rows of non-matching data to the result table.

Abstract: A query processing system operates by: 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.

Abstract: A query processing system operates by: 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.

Abstract: A database system is operable to determine a query for execution. The database system can execute a left join operation for the query based on receiving a plurality of left input rows, and forwarding all of the plurality of left input rows are forwarded. It is determined whether any right input rows match with each given left input row based on a hash map. When one right input row is identified as matching with the given left input row, a value of right input row is copied and emitted in conjunction with the given left input row. When no right input rows are identified as matching with the given left input row, a null value is emitted in conjunction with the given left input row.

Abstract: A database system is operable to determine a query for execution. The database system can execute a left join operation for the query based on receiving a plurality of left input rows, and forwarding all of the plurality of left input rows are forwarded. It is determined whether any right input rows match with each given left input row based on a hash map. When one right input row is identified as matching with the given left input row, a value of right input row is copied and emitted in conjunction with the given left input row. When no right input rows are identified as matching with the given left input row, a null value is emitted in conjunction with the given left input row.