Database Tool laggy and freeze

I was able to capture the following in the Activity Monitor right after the UI became responsive again:

%CPU Subsystem

158.9 <Process total CPU usage>
45.9 editor.impl.view (in com.intellij.openapi)
36.9 editor.impl (in com.intellij.openapi)
8.6 editor.ex.util (in com.intellij.openapi)
4.8 it.unimi.dsi.fastutil.ints
2.3 <unidentified: DefaultDispatcher-worker->
1.5 <Activity Monitor>
1.2 platform.core.nio.fs (in com.intellij)

Hello, @G1ZgY,

To check the issue, please create YouTrack ticket and attach the logs archive, which can be found under Help | Collect Logs and Diagnostic Data.

Problem description:

I am experiencing severe UI freezes in PyCharm Database Tools when working with a specific MySQL table containing JSON columns.

Environment:

• MySQL database
• PyCharm Professional (Database Tools plugin)
• Same behavior across multiple servers containing the same database/schema
• Other tables work normally

Table structure:

• Several numeric columns
• Timestamp column
• Two JSON columns

Observed behavior:

• Selecting rows from this table freezes the IDE UI for a long time
• Even fetching a small number of rows may cause the UI to hang
• Query execution on the MySQL side appears fast, but rendering/display in PyCharm becomes extremely slow
• The issue started recently; previously the same table worked normally

Investigation results:

• Queries excluding the problematic JSON column work fast
• Queries using truncated/casted JSON values work fast
• Queries selecting the raw JSON column cause severe freezes

This strongly suggests the issue is related to PyCharm/DataGrip JSON rendering/parsing rather than MySQL execution itself.

Additional findings:

• MySQL server performance appears normal
• LIMIT queries with small result sets are enough to reproduce the issue
• The problem reproduces only in PyCharm Database Tools
• The same data works correctly when JSON is converted to plain text or truncated before rendering

Example reproduction pattern:

SELECT
id,
created_at,
json_column
FROM some_table
ORDER BY id DESC
LIMIT 20;

Workaround that avoids freezes:

SELECT
id,
created_at,
LEFT(CAST(json_column AS CHAR), 1000) AS json_preview
FROM some_table
ORDER BY id DESC
LIMIT 20;

Hypothesis:
PyCharm/DataGrip may be performing expensive synchronous JSON parsing/rendering/tree-building for MySQL native JSON columns, causing UI thread freezes.

Could you please investigate possible regressions in JSON rendering/editor behavior in recent versions?

Hi G1ZgY, M9icokat,

I remember replying to both of your YouTrack tickets, so I assume you’re no longer experiencing this issue.

As a note in case someone else encounters this issue, the problem was fixed in DBE-25765, and the fix is included in IDE version 2026.1.1.

I've run into similar slowdowns with large JSON/JSONB columns. A practical workaround is to exclude those columns from the default query or limit the number of rows you're loading. If the issue still happens after updating PyCharm and the JDBC driver, it may be worth reporting it to JetBrains with a sample table or profiler logs so they can investigate.