Updated: April 19, 2023

Report virtual machine instructions for a command


 EXPLAIN sql-statement 


The EXPLAIN command modifier is a non-standard QDB extension. The idea comes from a similar command found in PostgreSQL, but the operation is completely different.

If the EXPLAIN keyword appears before any other QDB SQL command, then instead of actually executing the command, the QDB library reports the sequence of virtual machine (VM) instructions it would have used to execute the command had the EXPLAIN keyword not been present. This is useful for performance analysis.

For information about VM instructions, see the documentation on QDB opcodes.