RE: SQL statement PREPARE does not work in ECPG

Hi Matsumura-san,


Thank you for your explaining.

> An important point of the route is that it calls PQprepare() and PQprepare()
> needs type-Oid list. (Idea-1) If we fix for Prepare statement with AS clause and
> with parameter list to walk through the route, preprocessor must parse the parameter list and
> preprocessor or ecpglib must make type-Oid list. I think it's difficult.
> Especially, I wonder if it can treat user defined type and complex structure type.

I agree.
In the case of standard types, ECPG can get oids from pg_type.h.
However, in the case of user defined types, ECPG needs to access pg_type table and it is overhead.

Therefore, the second idea seems better.


By the way, should we support prepare statement like following?
(I think yes.)

============================
EXEC SQL PREPARE test_prep (int) AS SELECT id from test_table where id = :ID or id =$1;
============================

Current ECPG produces following code.

============================
ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "prepare \"test_prep\" ( int ) as \" select id from test_table where id
=$1  or id = $1 \"",
 
        ECPGt_int,&(ID),(long)1,(long)1,sizeof(int),
        ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EOIT, ECPGt_EORT);
============================


In this case, both ":ID" and "$1" in the original statement are converted to "$1" and ECPGdo() cannot distinguish
them.
Therefore, ECPG should produce different code.

For example, 
- ECPG convert ":ID" to "$1" and "$1" in the original statement to "$$1"
- next_insert() do not check "$$1"
- ECPGdo() reconvert "$$1" to "$1"



Regards,
Ryohei Takahashi