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TIBCOSoftware / snappy-store

SnappyStore
Apache License 2.0
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ComputeDB ODBC Driver returns incorrect Decimal values #527

Closed bisenpiyush closed 4 years ago

bisenpiyush commented 4 years ago

In Snappy C++ native client, to convert the decimal value into a string, the "mpz_sizeinbase" function of "GMP" library gets used, which returns the number of digits present in decimal value. As per its implementation, it could return the exact result or 1 too big. Since this function returns 1 too big (in other words, if there are 2 digits in decimal value, it returns the 3) which turns into the wrong result string. For example, if the column value is "0.66" then output is "6.6"

Changes proposed in this pull request

Added code to resolve the mpz_sizeinbase (GMP library) function's "1 too big" issue. Added "+2" for display size for data type decimal and numeric. Followed the Microsoft document on "Display size" for this change.(https://docs.microsoft.com/en-us/sql/odbc/reference/appendixes/display-size?view=sql-server-ver15)

Patch testing

Manual testing Unit test

Is precheckin with -Pstore clean?

NA

ReleaseNotes changes

NA

Other PRs

Unit test added in snappy-odbc branch https://github.com/SnappyDataInc/snappy-odbc/pull/13

nikhilbandi commented 4 years ago

Can the link to Microsoft documentation on "Display size" be provided as part of the section "Changes in this pull request"? Also, testing with large decimal digits and negative numbers should be carried out.

bisenpiyush commented 4 years ago

Can the link to Microsoft documentation on "Display size" be provided as part of the section "Changes in this pull request"? Added the link Also, testing with large decimal digits and negative numbers should be carried out. Manual testing has been done already for large decimal value ( for precision value more than 5) and for negative value as well ( for precision value 3, when the scale is 2)

bisenpiyush commented 4 years ago

Could you add a few unit tests for this code path (for example, test different decimal values)?

The respective unit test will get added into the unit test written for ODBC Driver in snappy-odbc branch and separate PR will get raised for it.