CODEWITHSUNDEEP
sqlpostgresqlconcurrency
Alienfluid
Alienfluid

Reputation: 326

Can records be inserted while the SELECT statement is executing in PostgreSQL?

I have a query that does something like this --

SELECT localtimestamp, x, y, z 
FROM table1 
WHERE updated_at > NOW() - INTERVAL '1 minute';

updated_at is defined to be set to the current_timestamp by default (in this case, I've verified that localtimestamp and current_timestamp are the same on the DB server).

Is it possible for this query to return records where updated_at > localtimestamp (the first field returned by the query)? In other words, can records be inserted into the table while the query is executing?

There are no explicit locks being acquired or transactions in the picture.

Upvotes: 1

Views: 59

Answers (1)

Nick Barnes
Nick Barnes

Reputation: 21336

Other inserts are allowed to happen, but your query won't see them.

From the documentation on isolation levels:

A statement can only see rows committed before it began. This is the default.

Upvotes: 2

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