Debugging read/write

This page describes reasons, why Heimdall might not use reader servers, when load balancing is enabled.

Show queryinfo

When using a tool that performs simple queries (i.e. not a prepared statement query) such as psql, after a query is executed, the command show queryinfo can be executed, which will provide information about the last query, and how it was processed, specifically the properties that were attributed to that command. An example output:

dbConsole => show queryinfo;

      Attribute       |        Value
----------------------+----------------------
forward:source        | MySQLDataSource
cache:ttl             | 300000
all:stop              | false
all:querytimeout      | 0
all:printtiming       | false
all:printtables       | false
all:printresults      | false
all:printmeta         | false
all:printmatch        | false
all:printcapture      | false
all:onlytrans         | false
all:olderthan         | 0
all:notrack           | false
all:maxburst          | 10
all:logger            | hdlog
all:log               | false
all:invalidate        | true
all:capture           | true
noreader              | forward:readonly is set to false, can't use reader
nocache reason        | cache is not enabled
connid                | 5
cache                 | true
autogenKeys           | true
Tables                | []
Source                | MySQLDataSource-Primary
Schema                | empty
RespTime              | 1779
DML                   | true
Catalog               | myDb
CacheHit              | miss
Autocommit            | true

noreader

noreader can have a few causes, they are explained in more detail in list below: