1. A method for querying a table, portions of the table being stored on respective processing modules, so that the table is stored across multiple processing modules, the method comprising: specifying module group characteristics; identifying a plurality of modules corresponding to the module group characteristics, the plurality of modules being less than all of the multiple processing modules where the table is stored; sampling the identified modules, but not sampling those modules among the multiple processing modules where the table is stored that are not among the identified modules, for statistics concerning the table specified in a query; optimizing an execution plan for the query based at least in part on the sampled statistics; determining a confidence level for the sampled statistics based at least in part on the ratio of the number of identified modules to the number of processing modules in a configuration, the number of processing modules across which the table is stored being less than or equal to the number of processing modules in the configuration, where the step of optimizing is based at least in part on the confidence level; and executing the optimized execution plan for the query.