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This demonstration showcases a system for visualizing and analyzing
search spaces generated by the SQL Anywhere optimizer during the
optimization process of a SQL statement. SQL Anywhere is a
relational database management system ( RDBMS ) whose optimizer uses
a left-deep tree join enumeration algorithm. The SQL Anywhere
dynamically optimizes each statement every time it is executed. The
decisions made by the optimizer during the optimization process are
both cost-based and heuristics adapted to the current state of the
server and the database instance. Many performance issues can be
understood and resolved by analyzing the search space generated when
optimizing a certain request. In our experience, there are two main
classes of performance issues related to the decisions made by a
query optimizer: (1) a request is very slow due to an unoptimal
access plan; and (2) a request has a different, less optimal access
plan than in a previous execution. We have enhanced SQL Anywhere to
log, in a very compact format, its search space during optimization
process when the tracing mode is on. Such search space logs can be
used in performance analysis without the database instances or extra
information about the SQL Anywhere server state at the time the logs
were generated. This demonstration introduces the
SearchSpaceAnalyzer system, a research prototype used to analyze the
search spaces of the SQL Anywhere optimizer. The system visualizes
and analyzes (1) a single search space and (2) the differences
between two search spaces generated for the same query by two
different optimization processes.