Increasing the accuracy and coverage of SQL progress indicators

Recently, progress indicators have been proposed for long-running SQL queries in RDBMSs. Although the proposed techniques work well for a subset of SQL queries, they are preliminary in the sense that (1) they cannot provide non-trivial estimates for some SQL queries, and (2) the provided estimates can be rather imprecise in certain cases. In this paper, we consider the problem of supporting non-trivial progress indicators for a wider class of SQL queries with more precise estimates. We present a set of techniques in achieving this goal. We report an initial implementation of these techniques in PostgreSQL.