Bug #117608 Connector/C 9.1 reports wrong sizes for TEXT columns

• Submitted: 2 Mar 17:10
• Reporter: Sruli Ganor
• Status: Open
• Category: Connector / C
• Severity: S1 (Critical)
• Version: 9.1
• OS: Windows
• CPU Architecture: Any

[2 Mar 17:10] Sruli Ganor

Description:
We read MySQL as raw data without charset conversions.
I.e. we set character_set_client=binary, character_set_connection=binary, character_set_results=NULL.
We do the conversion ourselves, so we must know the columns' metadata including column and display sizes.

In version 9.1, the Connector/C reports wrong sizes for these types if the database's charset is utf8mb4:
TINYTEXT:   Column Size: 63,      Display Size: 255
MEDIUMTEXT: Column Size: 4194303, Display Size: 16777215
LONGTEXT:   Column Size: 4GB,     Display Size: 4GB

These sizes are wrong and incompatible with the metadata returned by connector 8.0 for the same database:
TINYTEXT:   Column Size: 255,      Display Size: 63
MEDIUMTEXT: Column Size: 16777215, Display Size: 4194303
LONGTEXT:   Column Size: 4GB,      Display Size: 1GB

This seems to be a bug and it critical for us.
Thanks
 

How to repeat:
We have a test program that reproduces the issue.
I'll be glad to provide it uopn request.

In summary, the programs connecst to a MySQL utf8mb4 database, sets binary mode, and gets the metadata of the various TEXT columns as follows:

SQLDescribeColW(hStmt, colIndex, colName,..., &dataType, &columnSize, ...); 
SQLColAttributeW(hStmt, colIndex, SQL_DESC_DISPLAY_SIZE, ..., &displaySize);

Then it prints columnSize and displaySize.

When running the same program on the same database, while only changing the driver version, the printed sizes are different.

Suggested fix:
Make the size compatible with previous connector version.