Chapter 3. Understanding VoltDB Execution Plans


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Chapter 3. Understanding VoltDB Execution Plans

This chapter explains how VoltDB plans for executing SQL statements, the information it generates about the plans, and how you can use that information to evaluate and optimize your SQL code.

3.1. How VoltDB Selects Execution Plans for Individual SQL Statements

When VoltDB parses a stored procedure definition or an ad hoc query, it reviews possible execution plans for the SQL statements involved. Based on the schema, the partition columns, and any implicit or explicit indexes for the tables, VoltDB chooses what it believes is the most efficient plan for executing each statement. The more complex the SQL statement, the more execution plans VoltDB considers.

As part of the compilation process, VoltDB generates explain or execution plans that you can use to understand what execution order was selected. You can also affect those plans by specifying the order in which tables are joined as part of your SQL statement declaration.