Add an option to convert numbers between double and decimal in the same way as node.js, python3, ruby, rust or so about odpi HOT 5 OPEN

It's not zhat easy: insert 191/200 in Oracle DB into a num NUMBER column.
That's 0.955.
Then SELECT num-0.955 FROM table.
That will be 10^-39.

I don't think that hiding this in a driver would do any good...

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@tgulacsi
Could you post details? What programming language or tool did you use? How did you insert and fetch numbers?
I cannot reproduce it by sqlplus and rust-oracle.

I think that the inserted value is not 0.955.
If it is exactly 0.955, SELECT dump(num) FROM table is Typ=2 Len=3: 192,96,51.
I guess that dump(num) is Typ=2 Len=21: 192,96,51,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,?? (0.95500000000000000000000000000000000000??) in the your table because num-0.955 is 10^-39.

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You're right, it depends on the column's data type - NUMBER works as expected,
but if you specify a precision, it degrades to using floating-point:

CREATE TABLE w_gt_test_n (n NUMBER, n38 NUMBER(38,38)) TABLESPACE DATA;
INSERT INTO W_gt_test_n VALUES (0.955, 0.955);
INSERT INTO W_gt_test_n VALUES (191/200, 191/200);
SELECT n, DUMP(n), n38, DUMP(n38), DUMP(n-n38) FROM w_gt_test_n;
DROP TABLE w_gt_test_n;

PL/SQL Developer (Delphi):

N	DUMP(N)	N38	DUMP(N38)	DUMP(N-N38)
0,955	Typ=2 Len=3: 192,96,51	0,95500000000000013	Typ=2 Len=3: 192,96,51	Typ=2 Len=1: 128
0,955	Typ=2 Len=3: 192,96,51	0,95500000000000013	Typ=2 Len=3: 192,96,51	Typ=2 Len=1: 128

SQL*Plus:

         N
----------
DUMP(N)
--------------------------------------------------------------------------------
       N38
----------
DUMP(N38)
--------------------------------------------------------------------------------
DUMP(N-N38)
--------------------------------------------------------------------------------
      ,955
Typ=2 Len=3: 192,96,51
      ,955
Typ=2 Len=3: 192,96,51
Typ=2 Len=1: 128

      ,955
Typ=2 Len=3: 192,96,51
      ,955
Typ=2 Len=3: 192,96,51
Typ=2 Len=1: 128

So yes, I've also fallen: it's only the displaying library's error.

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I think that the feature is useful for node-oracledb. But it isn't for cx_Oracle (if I don't misunderstand this) and rust-oracle because they use DPI_NATIVE_TYPE_BYTES for numbers and access numbers via strings.
If it isn't useful for drivers other than what I checked, feel free to close it. If only one driver needs it, it is almost dead code.

Well, I thought that cx_Python also used DPI_NATIVE_TYPE_DOUBLE for numbers as node-oracledb did and it was worth to add the feature. But cx_Python have used DPI_NATIVE_TYPE_BYTES for numbers since this commit. I'm not sure now whether it is worth or not.

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We'll definitely evaluate it.

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