Reg postgresSQL source code

Dear Sir,

I am a 3rd year B.Tech. (Computer Science Engineering) student at IIIT,
Hyderabad (India). For the past 5 months I've been trying to implement a
module in postgresSQL and I am stuck at a point.
I'll be highly grateful to you if you could help me out.

The module is about constructing a new plan without calling the optimizer.
The new plan should be built using some old available plans and the
parsetree of the new query. It is assumed that the new plan and old plan
have similar structure.

Doubt:
I am not able to figure out the meaning of 'targetlist' in the 'plan'
node. Earlier I thought it was a list of TargetEntry nodes that contains
the information about the column names in the SELECT clause. But the
subplans (i.e., 'lefttree' and 'righttree' nodes) again contain the
targetlist and I want to know about them.

Could you please also let me know if there is a way in which I can
construct these targetlists using just the parsetree of the query and not
any other information like "context" or "outPlan".

Thank You
Manan Nayak
B.Tech. (CSE)
IIIT, Hyderabad

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