When I create a report that contains both a table and a chart (of the same data set), the preview render is incredibly slow, database server churns amazingly. Haven't tried this in production, yet ... I'm afraid to!

Here are some numbers, to give you scale on those adverbs:

To retrieve the data set directly from the database (command-line mysql):
- 4.92 seconds
- mysqld running the whole time at 98% CPU

To retrieve the data set into the BIRT Data Set preview (in the Data Set Editor):
- 10 seconds
- mysqld: 98% CPU

To render a report containing only the table of values:
- 11 seconds / 98%

To render a report containing only the chart of values:
- 12 seconds / 98%

OK, those are all within reasonable range of each other. But now:

To render a report containing both a table and a chart of the same data set:
- 140 seconds
- mysqld churning at 180% CPU (it's a 2-core system)

I don't seem to by doing much disc I/O during that long processing.

I'm forced to suspect that the table-plus-chart report is posting the query many times, not just once or twice. Or, perhaps it's removing part of my query?

Might this be some botch in the way I created the report? Is there something else I can do about it?

Some of those details that make life worthwhile:

All operations (database, Eclipse) on one box:
- 2.66 GHz Intel Core 2 Duo, 8GB RAM, SSD
BIRT: 2.5.1.v20090624
Eclipse: 3.5.1.R35x_v2009
MySQL: 5.1.37
JDBC: mysql-connector-java-5.1.10-bin.jar

Query:

(yes, the "limit 20" is in the query defined in the Data Set Editor, and I notice the editor doesn't color-code "limit 20" as if it knew it was SQL)

rows in table access: about 7M
rows in the data set if you remove the limit: 201
Time to do the unlimited query from command-line: 128 seconds

So I guess the "render report with both table and chart" time is roughly comparable to the "query without the limit clause" time, and maybe the problem is not multiple queries but incomplete query spec?