Tom Lane wrote on 16.07.2010 18:40:
Thomas Kellerer<spam_eater@xxxxxxx> writes:
the explanation of the --inserts option of pg_dumps states that
"The --column-inserts option is safe against column order changes, though even slower."
The way I read this is, that
INSERT INTO table (column, ...) VALUES ...
is slower than
INSERT INTO table VALUES ...
Is that really true?
I believe so, though I've not measured by how much.
Why would explicitely stating the columns be slower than relying on implicit column ordering?
Well, first off, the volume of pg_dump'd data gets a lot larger due to
all the extra text. If your column values aren't textually wide, you
could easily be looking at 2x the space. That costs in I/O and network
transmission.
Of course
In the second place, it does take time to parse those
column names and look them up in the catalog. Not much, but it'll add
up since it's done over again for every row.
Hmm.
For years I have been advocating to always use fully qualified column lists in INSERTs (for clarity and stability)
And now I learn it's slower when I do so :(
Thomas
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