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.
