Best way to check if a table is empty

[Marcelo Fernandes]

Hi folks,

I came up with three strategies to verify whether a table is empty.

I wanted to sound the community to check whether my assumptions are correct for
each of these strategies, and to also discuss which strategy is best.

## Strategy 1 [possibly best?]

SELECT EXISTS (SELECT 1 FROM foo LIMIT 1);

Pros:
  1. Works with any table.
  2. Relatively fast (if the table is well organised).

Cons:
  1. Sequential Scan
  2. If the table is bloated, it reads more buffers.

## Strategy 2

SELECT min(id) FROM foo;

Pros:
  1. Does an index-only scan on a field that presumably has a PK index.
  2. Works well even if the table is bloated.

Cons:
  1. Sequential Scan if the table does not have a PK index.
  2. Reads a few more buffers than Strategy 1 when the table is well organised.
  3. Performs worse if the index is bloated.

## Strategy 3 [worst]

SELECT count(*) FROM foo;

Pros:
  1. Uses a widespread and intuitive operation (count)

Cons:
  1. Very slow on large tables as it performs a Sequential Scan.


How does all of that sound? Are there further strategies I should consider?
Anything I have missed in the Strategies above?

Regards,
Marcelo.