GitHub user jianqiao opened a pull request:

    Optimizer changes for the LIPFilter feature.

    There will be three PRs for adding the _LIPFilter_ feature: optimizer 
changes / execution generator changes / relational operator changes. This is 
the first PR that does optimizer changes.
    LIP (lookahead information passing) filter is an improved semi-join 
optimization technique that pushes "future selectivities" down a left-deep 
query plan tree. For linear / bush trees, we can also search for the left-deep 
pattern in the tree and apply the LIP filter optimization.
    With LIP, the overall SSB benchmark (scale factor 100) performance will be 
improved from ~19 seconds to ~12 seconds on the cloudlab machine. The TPC-H 
benchmark performance will also be improved greatly (e.g. `Q02 6.7s -> 0.7s, 
Q17 166s -> 1.7s, Q20 55s -> 1.7s`).
    Main changes in this PR:
    (1) Rewrote `StarSchemaHashJoinOrderOptimization`. This changed some of the 
TPC-H query plans. One or two SSB query plans were also slightly changed due to 
an adjustment in `StarSchemaSimpleCostModel`. Nevertheless we will achieve an 
overall performance of ~12 seconds for the SSB benchmark when the full feature 
is there.
    (2) Added a `LIPFilterConfiguration` data structure to store the LIP filter 
information during query optimization.
    (3) Implemented optimizer rule `AttachLIPFilters` to decide and attach LIP 
filters to the physical query plan.

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Alternatively you can review and apply these changes as the patch at:

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #113
commit 8740f50a710d0390155dc3a9a68dbbc2abe2cb7f
Author: Jianqiao Zhu <>
Date:   2016-09-07T18:20:43Z

    Optimizer changes for the LIPFilter feature.


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