MySQL Bugs: #120964: Index was out of range error triggered by autocomplete while typing qualified column names in SQL editor

Bug #120964	Index was out of range error triggered by autocomplete while typing qualified column names in SQL editor
Submitted:	20 Jul 17:16
Reporter:	Atul soni	Email Updates:
Status:	Won't Fix	Impact on me:	None
Category:	MySQL Workbench	Severity:	S3 (Non-critical)
Version:	8.0.44	OS:	Windows (Windows 11, 64-bit)
Assigned to:		CPU Architecture:	Any

Description:
While typing a comma-separated list of qualified column names in the SQL
editor (e.g. table.column, table.column, table.column), MySQL Workbench
crashes with an unhandled exception:

"Index was out of range. Must be non-negative and less than the size
of the collection. Parameter name: index"

This appears related to Bug #97444 (Closing query tab while query runs
in other tab may trigger index out of range), which reports the same
underlying error message from a different trigger (closing a query
tab while another query is running). In my case, the trigger is the
autocomplete/code-completion feature reacting to typed input in the
SQL editor, not tab closure.

Expected Result:
Autocomplete should either show relevant suggestions or fail silently,
without crashing the editor.

Actual Result:
Application throws an unhandled exception dialog: "Index was out of
range. Must be non-negative and less than the size of the collection.
Parameter name: index"

How to repeat:
1. Open a SQL editor tab connected to a schema with multiple tables
   (e.g. customers, orders).
2. Begin typing a SELECT statement with a comma-separated list of
   qualified column names, such as:
   customers.customerName, orders.orderNumber, orders.orderDate
3. As autocomplete suggestions pop up while typing, the application
   throws the "Index was out of range" exception and shows the crash
   dialog.

Workaround: disabling Edit > Preferences > SQL Editor > "Enable Code
Completion in the Editor" prevents the crash.

This error occurred again today under the same conditions - typing a comma-separated list of qualified column names (table.colum

Attachment: Screenshot 2026-07-20 225149.png (image/png, text), 111.51 KiB.

Posted by developer:

This issue applies to the legacy MySQL Workbench 8.x implementation that is no longer supported or maintained.
MySQL Workbench 26.7 is a complete rewrite using a new technology stack and does not use the affected legacy implementation.
Therefore, this issue is not applicable to the current MySQL Workbench product and as such is closed.