Re: pg_locks-exclusivelock for select queries

On Fri, 2024-03-22 at 12:43 +0530, arun chirappurath wrote:
> I am running below query on a database. why is it creating a exclusive lock on a virtualxid?
> I am running some SELECT queries and its creating an ExclusiveLock in virtualxid? is this normal?
>
> SELECT datname, pid, state, query, age(clock_timestamp(), query_start) AS age
> FROM pg_stat_activity
> WHERE state <> 'idle'
>     --AND query NOT LIKE '% FROM pg_stat_activity %'
> ORDER BY age;
>
> |locktype  |database|relation|page|tuple|virtualxid|transactionid|classid|objid|objsubid|virtualtransaction|pid 
 |mode          |granted|fastpath|waitstart| 
>
|----------|--------|--------|----|-----|----------|-------------|-------|-----|--------|------------------|------|---------------|-------|--------|---------|
> |relation  |58,007  |12,073  |    |     |          |             |       |     |        |5/165           
 |21,912|AccessShareLock|true  |true    |         | 
> |virtualxid|        |        |    |     |5/165     |             |       |     |        |5/165           
 |21,912|ExclusiveLock |true   |true    |         | 

That's normal.  Every transaction has an exclusive lock on its own transaction ID.

Yours,
Laurenz Albe