Report VM instructions for a command
The EXPLAIN command modifier is a non-standard 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 will report back the sequence of virtual machine instructions it would have used to execute the command had the EXPLAIN keyword not been present. This is useful for performance analysis.
For additional information about virtual machine instructions see the documentation on QDB opcodes for the virtual machine.