Migrating from Oracle - Implicit Casting Issue

On Monday, July 18, 2022, Karthik K L V <venkata.karthik4u@gmail.com> wrote:

Hi Team,

We are migrating from Oracle 12c to Aurora Postgres 13 and running into
implicit casting issues.

Oracle is able to implicitly cast the bind value of prepared statements
executed from the application to appropriate type - String -> Number,
String -> Date, Number -> String etc. when there is a mismatch b/w java
data type and the column Datatype.

For example: If the Datatype of a Column is defined as Number and the
application sends the bind value as a String (with single quotes in the
query) - Oracle DB is able to implicitly cast to Number and execute the
query and return the results.

The same is not true with Postgres and we are getting below exception

*org.postgresql.util.PSQLException: ERROR: operator does not exist: bigint
= character varying*
*Hint: No operator matches the given name and argument types. You might
need to add explicit type casts..*

We found a Postgres Driver property - stringtype=unspecified which appears
to solve this problem and have the following questions.
https://jdbc.postgresql.org/documentation/83/connect.html

Could you please let us know the following?

Q1) Will configuring this stringtype property introduce overhead on
Postgres leading to Performance issues
Q2)Does setting this attribute have any other implications on the data in
the DB.
Q3)Is there any plan to deprecate / stop supporting this attribute in
future Aurora Postgres releases.

That setting is not recognized by the server in any way, it is a driver
concern only. IIUC it makes the Java Driver behave in a way consistent
with the expectations of the server since by leaving the supplied type info
undeclared the server can use its own logic. If it works for you I say use
it, it will be less problematic than methodically fixing your queries up
front. Though if there are some that show to be bottlenecks getting the
type info correct may prove to make a difference in some situations.

David J.

Hi David,

Thanks for the quick response.
Making sure I got it right - U mean Postgres DB Server when you say server
right?
IIUC, by configuring this property, the driver will not set the type and
leave it to the Postgres DB Server to map it to the appropriate type. Will
this have any performance implication on the Postgres server that we need
to worry about?

Thanks,
Karthik K L V

On Tue, Jul 19, 2022 at 12:12 PM David G. Johnston <
david.g.johnston@gmail.com> wrote:

On Monday, July 18, 2022, Karthik K L V <venkata.karthik4u@gmail.com>
wrote:

Hi Team,

We are migrating from Oracle 12c to Aurora Postgres 13 and running into
implicit casting issues.

Oracle is able to implicitly cast the bind value of prepared statements
executed from the application to appropriate type - String -> Number,
String -> Date, Number -> String etc. when there is a mismatch b/w java
data type and the column Datatype.

For example: If the Datatype of a Column is defined as Number and the
application sends the bind value as a String (with single quotes in the
query) - Oracle DB is able to implicitly cast to Number and execute the
query and return the results.

The same is not true with Postgres and we are getting below exception

*org.postgresql.util.PSQLException: ERROR: operator does not exist:
bigint = character varying*
*Hint: No operator matches the given name and argument types. You might
need to add explicit type casts..*

We found a Postgres Driver property - stringtype=unspecified which
appears to solve this problem and have the following questions.
https://jdbc.postgresql.org/documentation/83/connect.html

Could you please let us know the following?

Q1) Will configuring this stringtype property introduce overhead on
Postgres leading to Performance issues
Q2)Does setting this attribute have any other implications on the data in
the DB.
Q3)Is there any plan to deprecate / stop supporting this attribute in
future Aurora Postgres releases.

That setting is not recognized by the server in any way, it is a driver
concern only. IIUC it makes the Java Driver behave in a way consistent
with the expectations of the server since by leaving the supplied type info
undeclared the server can use its own logic. If it works for you I say use
it, it will be less problematic than methodically fixing your queries up
front. Though if there are some that show to be bottlenecks getting the
type info correct may prove to make a difference in some situations.

David J.

--
Karthik klv