=== with indexes: milliseconds per query (1000 runs each)
queue of one outlet           0.018
one bill by its id            0.007
customer by phone             0.005
customer by phone digits      0.050
bills of March, by range      0.013
bills of March, by SUBSTR     0.224

=== without indexes: milliseconds per query (1000 runs each)
queue of one outlet           0.218
one bill by its id            0.007
customer by phone             0.016
customer by phone digits      0.041
bills of March, by range      0.235
bills of March, by SUBSTR     0.218

