Bernd Helmle wrote:
--On Mittwoch, Mai 06, 2009 19:04:21 -0400 Tom Lane <t...@sss.pgh.pa.us>
wrote:
So I'm now persuaded that a better textual representation for bytea
should indeed make things noticeably better here. It would be
useful though to cross-check this thought by profiling a case that
dumps a comparable volume of text data that contains no backslashes...
This is a profiling result of the same data converted into a printable
text format without any backslashes. The data amount is quite the same
and as you already guessed, calls to appendBinaryStringInfo() and
friends gives the expected numbers:
time seconds seconds calls s/call s/call name
35.13 24.67 24.67 134488 0.00 0.00 byteaout
32.61 47.57 22.90 134488 0.00 0.00 CopyOneRowTo
28.92 67.88 20.31 85967 0.00 0.00 pglz_decompress
0.67 68.35 0.47 4955300 0.00 0.00
hash_search_with_hash_value
0.28 68.55 0.20 11643046 0.00 0.00 LWLockRelease
0.28 68.75 0.20 4828896 0.00 0.00 index_getnext
0.24 68.92 0.17 1208577 0.00 0.00 StrategyGetBuffer
0.23 69.08 0.16 11643046 0.00 0.00 LWLockAcquire
...
0.00 70.23 0.00 134498 0.00 0.00 enlargeStringInfo
0.00 70.23 0.00 134497 0.00 0.00 appendBinaryStringInfo
0.00 70.23 0.00 134490 0.00 0.00 AllocSetReset
0.00 70.23 0.00 134490 0.00 0.00 resetStringInfo
0.00 70.23 0.00 134488 0.00 0.00 CopySendChar
0.00 70.23 0.00 134488 0.00 0.00 CopySendEndOfRow
while doing some pg_migrator testing I noticed that dumping a database
seems to be much slower than IO-system is capable off. ie i get 100% CPU
usage with no IO-wait at all with between 15-30MB/s read rate if i say
do a pg_dumpall > /dev/null.
The profile for that looks like:
samples % image name symbol name
1333764 29.3986 postgres CopyOneRowTo
463205 10.2099 postgres enlargeStringInfo
237117 5.2265 postgres AllocSetAlloc
231017 5.0920 postgres appendBinaryStringInfo
224792 4.9548 postgres heap_deform_tuple
172154 3.7946 postgres AllocSetReset
162434 3.5803 postgres DoCopyTo
149948 3.3051 postgres internal_putbytes
137548 3.0318 postgres OutputFunctionCall
129480 2.8540 postgres heapgettup_pagemode
101017 2.2266 postgres FunctionCall1
93584 2.0628 postgres pq_putmessage
86553 1.9078 postgres timesub
81400 1.7942 postgres CopySendChar
81230 1.7905 postgres int4out
78374 1.7275 postgres localsub
52003 1.1462 postgres MemoryContextAlloc
51265 1.1300 postgres CopySendEndOfRow
49849 1.0988 postgres SPI_push_conditional
48157 1.0615 postgres pg_server_to_client
47670 1.0507 postgres timestamptz_out
42762 0.9426 postgres timestamp2tm
Stefan
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