Option sql_vdbe_max_steps stops long running
queries from blocking tx thread or queries that 
use too much memory during local execution. 

Each sql query is compiled into VDBE opcodes on storages. This
parameter sets max number of opcodes that VDBE
can execute.

Example: `select * from t option(sql_vdbe_max_steps=1000)`

Option vtable_max_rows limits the maximum number of rows in
virtual table. This limit is checked on storages before returning
intermediate results and on routers when receiving results from
storages.

Example: `select * from t option(vtable_max_rows=1000)`