Data Source Error : DataSource.Error: PostgreSQL: 53300: Exceeded session limit of 1

[Miguel_Rojo]

Hi Community,

Recently, a new error started appearing and is now breaking my Power BI Dataflow refreshes.

I’m sharing the details below in case anyone has encountered a similar issue or can suggest a solution.

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Scenario

• My Dataflow pulls data from a PostgreSQL database (Adobe Experience Platform – AEP Data Lake).
• I’m using the default Power Query connector: PostgreSQL.Database(server, database, [Query="..."])

• Until last week, everything was working correctly (I run weekly refreshes).
• However, since yesterday, all refreshes are failing almost immediately (after ~15–45 seconds) with the following error:
  • Data Source Error: PostgreSQL: 53300: Exceeded session limit of 1 MashupValueException
  •  RootActivityId = f81d8c6f-9432-48fd-9138-a7b8238fb1f6     Request ID: 4cb3ff61-fecc-7091-670f-8c2e78f4b0e6

Key observation (critical)

To isolate the issue:

• I removed all transformations
• I executed only a single native SQL query

👉 The same error still occurs.

       So the issue is not related to transformation complexity or query size.

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Questions

1. Even when executing a single native SQL query via PostgreSQL.Database(),
   does Power Query internally require multiple sessions (e.g., for metadata, validation, or parallel evaluation)?

   • (i'm assuming that session/connection limit on the PostgreSQL endpoint has been reduced, but I still need to confirm with my company)

2. Has anyone experienced a similar issue when a strict session/connection limit was enforced on the database?

3. Have you implemented a strategy to solve this issue??

[tayloramy]

Hi @Miguel_Rojo, 

Power Query will make multiple connection attempts to the data source. There's usually one to list objects or schemas, one to get column names, and then one to get actual data. Sometimes there can be more depending on your query. 

It does sound like some settings changed on your source side, hopefully you can get those reverted so your dataflow will continue to work. 

[v-hjannapu]

Hi @Miguel_Rojo,

Thank you for reaching out to the Microsoft Community Forum.

The 53300: Exceeded session limit of 1 error suggests this is more likely coming from the PostgreSQL/AEP side rather than from the Dataflow transformations themselves. Since the refresh still fails even with a single native SQL query and no transformations, your testing already rules out query complexity as the cause.

Power Query/Dataflows may still perform additional backend operations besides the main query, so a strict session limit of 1 can lead to this behavior. Since this was working previously, I would recommend checking with the team managing the PostgreSQL/AEP environment to see whether the session/connection limit was recently changed.

Hope this helps if you have any queries we are  happy to assist you further.
Regards,
Community Support Team.