Skip to content

feat(query): tenant DB in SHOW TRANSACTIONS / SHOW ACTIVE USERS + foreign-read UAF fix + precise stuck-drain diagnostics #1843

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
vpavicic merged 2 commits into from
Oct 20, 2026
Merged

feat(query): tenant DB in SHOW TRANSACTIONS / SHOW ACTIVE USERS + foreign-read UAF fix + precise stuck-drain diagnostics #1843

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
7c70cf3
docs: database columns in SHOW ACTIVE USERS INFO and SHOW TRANSACTION…
andrejtonev Oct 19, 2026
d26222f
docs(server-stats): login timestamp, username and database cells matc…
andrejtonev Oct 19, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
23 changes: 19 additions & 4 deletions pages/database-management/server-stats.mdx
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -367,7 +367,7 @@ SHOW BUILD INFO;

## Active users information

Running this query will provide information about currently logged-in Memgraph users and their session details.
Running this query lists one row per open session, including the session that runs it:

```cypher
SHOW ACTIVE USERS INFO;
Expand All @@ -379,8 +379,23 @@ Identical information can be obtained by executing the following command:
SHOW ACTIVE USERS;
```

| Column | Description |
|------------------------------|-----------------------------------------------------------------------------------------------------|
| username | The session's logged-in user, also when the session impersonates another user; an empty string for a session that connected while authentication was disabled. |
| session uuid | The session's unique ID. |
| login timestamp | The time of the session's most recent login, as a string with microseconds. When another user logs in on the same connection, this time and the `username` change and the `session uuid` stays the same. |
| database | The session's current database: the one selected with `USE DATABASE`, the one named when connecting, or otherwise the user's main database (`memgraph` by default). |
| database marked for deletion | `true` if the session's database was dropped with [`FORCE`](/database-management/multi-tenancy#drop-database-with-force), otherwise `false`. Such sessions, including ones with an open transaction, are closed within about 10 seconds. |

For example, after a second session runs `USE DATABASE analytics` and `analytics` is then dropped with `DROP DATABASE analytics FORCE`:

```cypher
SHOW ACTIVE USERS INFO;
```

```copy=false
| username | session uuid | login timestamp |
|----------|----------------------------------------|-----------------------|
| test | "550e8400-e29b-41d4-a716-446655440000" | "2024-08-03 18:53:00" |
| username | session uuid | login timestamp | database | database marked for deletion |
|-----------|----------------------------------------|------------------------------|-------------|------------------------------|
| "admin_u" | "f1082c78-82ff-4b87-a5c4-340060a04a02" | "2026-10-19 12:02:10.248993" | "analytics" | true |
| "admin_u" | "bf7a6fbd-64cc-475c-a82c-5c293dd8108d" | "2026-10-19 12:02:10.065680" | "memgraph" | false |
```
60 changes: 36 additions & 24 deletions pages/fundamentals/transactions.mdx
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -139,10 +139,10 @@ rows contains:

| Key | Description |
|---|---|
| `phase` | Current phase of snapshot creation: `EDGES`, `VERTICES`, `INDICES`, `CONSTRAINTS`, or `FINALIZING`. |
| `phase` | Current phase of snapshot creation: `edges`, `vertices`, `indices`, `constraints`, or `finalizing`; `idle` until the first phase starts. |
| `items_done` | Number of objects serialized in the current phase so far. |
| `items_total` | Total number of objects expected in the current phase. |
| `db_name` | Name of the database whose snapshot is being created. |
| `db_name` | Name of the database whose snapshot is being created. The `database` column shows the same value. |

The top-level `start_time` and `elapsed_ms` columns are populated for snapshot
rows as well, reflecting when the snapshot started.
Expand Down Expand Up @@ -181,19 +181,31 @@ map for these rows contains:
| `phase` | Current phase of the cycle: `unlink` (detach obsolete versions no active transaction can still see), `index_cleanup` (remove stale index and constraint entries — usually the most expensive phase), or `delete` (free the unlinked versions). |
| `trigger` | `periodic` for the background cycle, or `forced` for a `FREE MEMORY` query or a storage-mode switch. |
| `exclusive_lock` | `true` when the collection holds the storage lock exclusively and is therefore blocking all transactions. |
| `db_name` | Name of the database whose garbage is being collected. |
| `db_name` | Name of the database whose garbage is being collected. The `database` column shows the same value. |

The top-level `start_time` and `elapsed_ms` columns reflect when the collection
started; a large `elapsed_ms` is the clearest signal of a stuck collection. One
`gc` row appears per database that currently has a collection running.

```copy=false
memgraph> SHOW TRANSACTIONS;
+----------+----------------+------------------------+-----------+-------------------------------------------------------------------------------------------+-------------------------------+------------+
| username | transaction_id | query | status | metadata | start_time | elapsed_ms |
+----------+----------------+------------------------+-----------+-------------------------------------------------------------------------------------------+-------------------------------+------------+
| "" | "gc" | ["GARBAGE COLLECTION"] | "running" | {db_name: "memgraph", exclusive_lock: true, phase: "index_cleanup", trigger: "periodic"} | 2026-05-12T14:32:17.881Z[UTC] | 395 |
+----------+----------------+------------------------+-----------+-------------------------------------------------------------------------------------------+-------------------------------+------------+
For example, a `FREE MEMORY` query on the `tenant1` database starts a forced
collection. While that collection runs, run the following query from another
session:

```cypher
SHOW TRANSACTIONS;
```

The result lists the `FREE MEMORY` transaction and its `gc` row, both on
`tenant1`:

```plaintext copy=false
+----------+-----------------------+------------------------+-----------+---------------------------------------------------------------------------------+----------------------------------------+------------+------------+
| username | transaction_id | query | status | metadata | start_time | elapsed_ms | database |
+----------+-----------------------+------------------------+-----------+---------------------------------------------------------------------------------+----------------------------------------+------------+------------+
| "" | "9223372036854775814" | ["FREE MEMORY"] | "running" | {} | 2026-10-19 12:01:18.288170000[Etc/UTC] | 4 | "tenant1" |
| "" | "9223372036854775815" | ["SHOW TRANSACTIONS"] | "running" | {} | 2026-10-19 12:01:18.292917000[Etc/UTC] | 0 | "memgraph" |
| "" | "gc" | ["GARBAGE COLLECTION"] | "running" | {db_name: "tenant1", exclusive_lock: false, phase: "unlink", trigger: "forced"} | 2026-10-19 12:01:18.288188000[Etc/UTC] | 5 | "tenant1" |
+----------+-----------------------+------------------------+-----------+---------------------------------------------------------------------------------+----------------------------------------+------------+------------+
```

<Callout type="info">
Expand Down Expand Up @@ -401,42 +413,42 @@ Managing transactions is done by establishing a new connection to the database.
**Show and terminate transactions**

The output of the `SHOW TRANSACTIONS` command shows that a query is
currently being run as part of the transaction ID "9223372036854794885".
being run on the `memgraph` database as part of the transaction ID
"9223372036854775809".

```copy=false
memgraph> SHOW TRANSACTIONS;
+----------+-----------------------+-------------------------------------------+-----------+----------+-------------------------------+------------+
| username | transaction_id | query | status | metadata | start_time | elapsed_ms |
+----------+-----------------------+-------------------------------------------+-----------+----------+-------------------------------+------------+
| "" | "9223372036854794885" | ["CALL infinite.get() YIELD * RETURN *;"] | "running" | {} | 2026-05-12T14:32:00.000Z[UTC] | 18230 |
| "" | "9223372036854794896" | ["SHOW TRANSACTIONS"] | "running" | {} | 2026-05-12T14:32:18.230Z[UTC] | 0 |
+----------+-----------------------+-------------------------------------------+-----------+----------+-------------------------------+------------+
+----------+-----------------------+-------------------------------------------------------------------------------------------+-----------+----------+----------------------------------------+------------+------------+
| username | transaction_id | query | status | metadata | start_time | elapsed_ms | database |
+----------+-----------------------+-------------------------------------------------------------------------------------------+-----------+----------+----------------------------------------+------------+------------+
| "" | "9223372036854775810" | ["SHOW TRANSACTIONS"] | "running" | {} | 2026-10-19 12:11:16.345268000[Etc/UTC] | 0 | "memgraph" |
| "" | "9223372036854775809" | ["UNWIND range(1, 100000) AS a UNWIND range(1, 100000) AS b WITH a WHERE a < 0 RETURN a"] | "running" | {} | 2026-10-19 12:11:14.342553000[Etc/UTC] | 2002 | "memgraph" |
+----------+-----------------------+-------------------------------------------------------------------------------------------+-----------+----------+----------------------------------------+------------+------------+
```

To terminate the transaction, run the following query:

```cypher
TERMINATE TRANSACTIONS "9223372036854794885";
TERMINATE TRANSACTIONS "9223372036854775809";
```

Upon the transaction termination, the following confirmation will appear:

```copy=false
memgraph> TERMINATE TRANSACTIONS "9223372036854794885";
memgraph> TERMINATE TRANSACTIONS "9223372036854775809";
+-----------------------+-----------------------+
| transaction_id | killed |
+-----------------------+-----------------------+
| "9223372036854794885" | true |
| "9223372036854775809" | true |
+-----------------------+-----------------------+
1 row in set (round trip in 0.000 sec)
```

The following message will appear in the session in which the infinite query was being run:
The following message will appear in the session in which the long-running query was being run:

```copy=false
memgraph> CALL infinite.get() YIELD * RETURN *;
Client received exception: Transactions was asked to abort either because it was executing longer than time
specified or another user asked to abort it.
memgraph> UNWIND range(1, 100000) AS a UNWIND range(1, 100000) AS b WITH a WHERE a < 0 RETURN a;
Client received query exception: Transaction was asked to abort by another user.
```

## Isolation levels
Expand Down
Loading