Till Westmann has posted comments on this change.

Change subject: Convert comparisons with current-datetime, current-date, and 
current-time to applicable index searches as though they were constants
......................................................................


Patch Set 1:

I think that it is important to evaluate the current-time at runtime as 
a) it is correct and 
b) it will come back to haunt us when we introduce prepared statements if we do 
it at compile-time now.

But I also think I understand Yingyi's concern. The solution in this patch is 
not so much based on rules but rather based on exceptions. Instead of creating 
a exceptional behavior for 3 functions, it would be nice to describe the 
properties of the expression that we need for the rewritings that were missing, 
and to build the rules based on those properties. It seems that the property of 
the expression that we are looking for is, that they return a constant value at 
runtime. It is a weaker property than a full constant expression, which is 
constant at compile-time as well and thus can be constant-folded in the 
optimizer. However, I think that this is the same property that a parameter to 
a prepared statment or a stored procedure would have. So I think that building 
the rules based on this property would also help for the implementation of 
stored procedures.

Does this make sense?

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Gerrit-MessageType: comment
Gerrit-Change-Id: Ied64276873afcfbdd31dac313009e47429d8f9b0
Gerrit-PatchSet: 1
Gerrit-Project: asterixdb
Gerrit-Branch: master
Gerrit-Owner: Steven Jacobs <[email protected]>
Gerrit-Reviewer: Jenkins <[email protected]>
Gerrit-Reviewer: Preston Carman <[email protected]>
Gerrit-Reviewer: Steven Jacobs <[email protected]>
Gerrit-Reviewer: Till Westmann <[email protected]>
Gerrit-Reviewer: Yingyi Bu <[email protected]>
Gerrit-HasComments: No

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