The garbagecollector should be the last optimizer in the pipe. Reconsider it putting it in the 'right' place On 10/08/16 12:08, Xu,Wenjian wrote:

Hi Martin,

On Wed, Aug 10, 2016 at 5:19 PM, Martin Kersten mailto:martin.kersten@cwi.nl> wrote:

On 10/08/16 10:49, Xu,Wenjian wrote:

Hi all,

MonetDB version: 11.23.7 Ubuntu version: 14.04

I created a new optimizer pipeline by adding an additional optimization step after 'default_pipe', i.e.: '*my_customized_pipe*'='optimizer.inline();optimizer.candidates();optimizer.remap();optimizer.costModel();optimizer.coercions();optimizer.evaluate();optimizer.pushselect();optimizer.aliases();optimizer.mitosis();optimizer.mergetable();optimizer.deadcode();optimizer.aliases();optimizer.constants();optimizer.commonTerms();optimizer.projectionpath();optimizer.deadcode();optimizer.reorder();optimizer.reduce();optimizer.matpack();optimizer.dataflow();optimizer.querylog();optimizer.multiplex();optimizer.generator();optimizer.profiler();optimizer.garbageCollector();*optimizer.customizedstep()*'

What I have done is: 1) Create an empty optimizer step: -- 1.1 add /opt_customizedstep.c/h/ in package /monetdb/optimizer/*/, leave function body /OPTcustomizedstepImplementation() /empty/, /i.e. with one statement */return 0*/ / -- /1.2 register the step by modifying /opt_wrapper.c /and/optimizer.mal/ 2) Add the definition of the new pipeline in /opt_pipes.c/ 3) Modify the configuration file to compile the added source files.

After re-build the system, I can enable the new optimizer pipeline by *set optimizer='my_customized_pipe'*. However, I have two issues:

i) using EXPLAIN statement, I found the MAL plan different from the one generated by 'default_pipe' (which should be the same since I did nothing in the added step?). Specifically, the plan seems to be not affected by /optimizer.reorder() /step, i.e., bat.new() and bat.append() instructions appear in the end of the plan.

1) make sure you restarted the server. 2) plans are cached, so if you attempt the following select count(*) from tables set optimizer='my_customized_pipe' select count(*) from tables

it still uses the default plan

Furthermore, the optimizer history is not saved unless you call DEBUG select....

I am sure that I have restarted the server. Also, I have excluded the factor of plan caching by *set optimizer='my_customized_pipe' *immediately after I entered the sql interface. But my problem is still there...

ii) then I entered mdb mode by DEBUG statement. But it seems that some command did not work as before. For example, *optimizer* command does not display actions performed by each optimizer step.

For this issue, I highly suspected that I have missed some steps to make a new pipeline work correctly...

Thank you very much for your kind reply.

Best regards, Wenjian

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