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Extensible executor nodes for preparation of SQL/MED

From: Itagaki Takahiro <itagaki(dot)takahiro(at)gmail(dot)com>
To: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Extensible executor nodes for preparation of SQL/MED
Date: 2010-10-25 11:16:49
Message-ID: (view raw or whole thread)
Lists: pgsql-hackers
SQL/MED will have some kinds of planner hooks to support FDW-depending
plan execution. Then, we will need to support user-defined executor nodes.
The proposed SQL/MED has own "executor node hooks" in ForeignTableScan,
but I think it will be cleaner to support it in executor level.

The attached patch is an experimental code to do it; Plan struct has
"vtable" field as a set of functions to generate and execute PlanState
nodes. It changes large switch-case blocks in the current executor
into function-pointer calls as like as virtual functions in C++.

Is it worth doing? If we will go to the direction, I'll continue to
research it, like extensibility of Path nodes and EXPLAIN support.

-------- Essence of the patch --------
typedef struct Plan
    NodeTag     type;
    PlanVTable *vtable;	/* executor procs */

struct PlanVTable
    ExecInitNode_type   InitNode;
    ExecProcNode_type   ProcNode;
    MultiProcNode_type  MultiProcNode;
    ExecEndNode_type    EndNode;

    node = makeNode(SeqScan);
    node->vtable = &SeqScanVTable;



Itagaki Takahiro

Attachment: extensible_execnodes-20101025.patch.gz
Description: application/x-gzip (12.0 KB)


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