Обсуждение: Two small questions re/ COPY CSV data into table
Hello,
I'm using COPY to load CSV data into the table in PG 10.x and have to simple
questions:
1. I do use as command:
COPY adm_cat FROM '/home/sisis/PostgreSQL/PDcsv/adm_cat.load' WITH DELIMITER '|' CSV ;
which works fine. When I read the PG docs the syntax should be
... WITH DELIMITER '|', FORMAT CSV ;
But this gives an syntax error as:
LINE 1: .../PostgreSQL/PDcsv/adm_cat.load' WITH DELIMITER '|', FORMAT C...
and the ',' is marked as its place. Why?
2. The CSV export is done by some Sybase tool which escapes the
delimiter as '\|', i.e. putting a backslash before the delimiter. I
found no way that COPY understands this excaping. Any ideas?
Thanks
matthias
--
Matthias Apitz, ✉ guru@unixarea.de, http://www.unixarea.de/ +49-176-38902045
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>>>>> "Matthias" == Matthias Apitz <guru@unixarea.de> writes: Matthias> ... WITH DELIMITER '|', FORMAT CSV ; I think you misread the docs; the new-style syntax would be COPY ... WITH (DELIMITER '|', FORMAT CSV); where the parens are not optional. The old-style syntax with no parens after WITH is what you were using before. Matthias> 2. The CSV export is done by some Sybase tool which escapes Matthias> the delimiter as '\|', i.e. putting a backslash before the Matthias> delimiter. I found no way that COPY understands this Matthias> excaping. Any ideas? That sounds like the file is not actually a CSV - why do you think it is? PG accepts two formats (actually 3 if you count binary format which is rarely used): TEXT: records are delimited by newlines, columns are delimited by a delimiter character (default tab), there are no quotation marks, any newline, backslash, or delimiter in the data must be escaped as a backslash-sequence (e.g. \n or \012) CSV: columns may be quoted (in which case delimiters and newlines inside them are ignored), records are delimited by newlines _outside_ quoted fields, there are no backslash-sequences or escapes outside of quoted fields, quote characters inside quoted fields are doubled (though there's an option to change this). PG follows the CSV spec at https://www.ietf.org/rfc/rfc4180.txt fairly closely. -- Andrew (irc:RhodiumToad)
El día Tuesday, June 04, 2019 a las 11:32:45AM +0100, Andrew Gierth escribió:
> Matthias> 2. The CSV export is done by some Sybase tool which escapes
> Matthias> the delimiter as '\|', i.e. putting a backslash before the
> Matthias> delimiter. I found no way that COPY understands this
> Matthias> excaping. Any ideas?
>
> That sounds like the file is not actually a CSV - why do you think it
> is?
>
> ...
Well, it's not strictly CSV, but it is what the Sybase tool produces. The
delimiter is set to '|' and a data example line looks like:
0|1| cat $1 \| lpr -Pprinter |3|4
I do load this now with COPY in mode TEXT and modify the data before
with:
sed 's/|/\v/g' < table-from-Sybase | sed 's/\\\v/|/g' > table-for-copy
Works fine.
matthias
--
Matthias Apitz, ✉ guru@unixarea.de, http://www.unixarea.de/ +49-176-38902045
Public GnuPG key: http://www.unixarea.de/key.pub
May, 9: Спаси́бо освободители! Thank you very much, Russian liberators!
>>>>> "Matthias" == Matthias Apitz <guru@unixarea.de> writes: >> That sounds like the file is not actually a CSV - why do you think >> it is? Matthias> Well, it's not strictly CSV, In other words it's not a CSV at all. Matthias> I do load this now with COPY in mode TEXT and modify the data Matthias> before with: Matthias> sed 's/|/\v/g' < table-from-Sybase | sed 's/\\\v/|/g' > table-for-copy What on earth is this supposed to achieve? -- Andrew (irc:RhodiumToad)
El día Tuesday, June 04, 2019 a las 04:41:47PM +0100, Andrew Gierth escribió:
> Matthias> I do load this now with COPY in mode TEXT and modify the data
> Matthias> before with:
>
> Matthias> sed 's/|/\v/g' < table-from-Sybase | sed 's/\\\v/|/g' > table-for-copy
>
> What on earth is this supposed to achieve?
It first translates any char '|' to vtab and then any '\vtab' (i.e. a
backslash followed by a vtab) back to the char |
The new DELIMITER for PG is then vtab and the | is just a char in the
data (in the example above a pipe of two UNIX cmd). Do you do UNIX?
matthias
--
Matthias Apitz, ✉ guru@unixarea.de, http://www.unixarea.de/ +49-176-38902045
Public GnuPG key: http://www.unixarea.de/key.pub
May, 9: Спаси́бо освободители! Thank you very much, Russian liberators!
>>>>> "Matthias" == Matthias Apitz <guru@unixarea.de> writes: Matthias> sed 's/|/\v/g' < table-from-Sybase | sed 's/\\\v/|/g' > table-for-copy >> What on earth is this supposed to achieve? Matthias> It first translates any char '|' to vtab and then any '\vtab' Matthias> (i.e. a backslash followed by a vtab) back to the char | Matthias> The new DELIMITER for PG is then vtab and the | is just a char in the Matthias> data (in the example above a pipe of two UNIX cmd). Yes, but why? If you use COPY ... WITH DELIMITER '|' (i.e. text mode, not CSV mode) then the \| is accepted as being a literal | and the unescaped | is treated as a delimiter. What is the point of the substitutions? -- Andrew (irc:RhodiumToad)
El día Tuesday, June 04, 2019 a las 05:56:49PM +0100, Andrew Gierth escribió:
> Matthias> The new DELIMITER for PG is then vtab and the | is just a char in the
> Matthias> data (in the example above a pipe of two UNIX cmd).
>
> Yes, but why?
>
> If you use COPY ... WITH DELIMITER '|' (i.e. text mode, not CSV mode)
> then the \| is accepted as being a literal | and the unescaped | is
> treated as a delimiter. What is the point of the substitutions?
In the original data record in Sybase there is a column containing, i.e.
some UNIX print command to be read and executed by the application:
cmd | lpr ...
it is exported into the file as
cmd \| lpr ...
because the export delimiter is set to '|';
the COPY in text mode was complaining because it interpreted the |
of the sequence \| as an delimiter and the number of columns did not
matched.
I will provide tomorrow the exact input line, the exact COPY command and
the error.
matthias
--
Matthias Apitz, ✉ guru@unixarea.de, http://www.unixarea.de/ +49-176-38902045
Public GnuPG key: http://www.unixarea.de/key.pub
May, 9: Спаси́бо освободители! Thank you very much, Russian liberators!
>>>>> "Matthias" == Matthias Apitz <guru@unixarea.de> writes: Matthias> it is exported into the file as Matthias> cmd \| lpr ... Matthias> because the export delimiter is set to '|'; Matthias> the COPY in text mode was complaining because it interpreted Matthias> the | of the sequence \| as an delimiter and the number of Matthias> columns did not matched. Matthias> I will provide tomorrow the exact input line, the exact COPY Matthias> command and the error. This worked for me: postgres=# copy ct(a,b,c,d,e) from stdin with delimiter '|'; Enter data to be copied followed by a newline. End with a backslash and a period on a line by itself, or an EOF signal. >> 0|1| cat $1 \| lpr -Pprinter |3|4 >> \. COPY 1 -- Andrew (irc:RhodiumToad)
Mathias:
On Tue, Jun 4, 2019 at 8:35 PM Matthias Apitz <guru@unixarea.de> wrote:
> El día Tuesday, June 04, 2019 a las 05:41:43PM +0200, Francisco Olarte escribió:
> > On Tue, Jun 4, 2019 at 5:03 PM Matthias Apitz <guru@unixarea.de> wrote:
> > > Well, it's not strictly CSV, but it is what the Sybase tool produces. The
> > > delimiter is set to '|' and a data example line looks like:
> > > 0|1| cat $1 \| lpr -Pprinter |3|4
> > > I do load this now with COPY in mode TEXT and modify the data before
> > > with:
> > > sed 's/|/\v/g' < table-from-Sybase | sed 's/\\\v/|/g' > table-for-copy
> > You are lucky it is not CSV, it is much better, it's similar to the
> > text format originally used by postgres. Your problem is just it uses
> > | instead of TAB for field delimiter.
> > What I d not know is why you use \v, doesn't sed use \t for TAB?
> I was thinking about \t and was afraid, that in ~2 GByte char fields
> even some \t could be used in the data. That's why I decided to use \v
> which is more unlikely to be used in our data.
Fine then. I haven't got much sed-foo under my belt, but if you do
this in perl ( I learned perl a while ago, forgot all awk and sed to
free some brain cells ;-> ) or something similar you can use high code
points or control chars ( and I do not know if sed can do several
replacements in a pass, but perl certainly can ). Something like (
untested ) "perl -pe 's/\\\\/\001/g; s/\\\|/\002/; s/\|/\t/;
s/\002/|/; s/\001/\\\\/", the advantage over the pipe approach may be
noticeable on big files, as it cuts a lot of context switches ( OTOH
it'll run single-core ).
( the sample tries to do
scaped backslash to soh
scaped pipe to stx
pipe to tab
stx to unescaped pipe
soh to escaped backlash
)
In fact you can do "tab to backslash t" after phase 2 and tab would be
ok in the input.
But, as I said before and others have also pointed, COPY is perfectly
happy to use pipe as delimiter and havinf it escaped with backslash on
input.
> (You didn't cc'ed the list, by intention?)
No, I forgot to hit reply-all because I did not pay enough attention,
my fault. Doing it now in case some one thinks this is interesting.
Francisco Olarte.
El día Tuesday, June 04, 2019 a las 07:20:54PM +0200, Matthias Apitz escribió:
> El día Tuesday, June 04, 2019 a las 05:56:49PM +0100, Andrew Gierth escribió:
>
> > If you use COPY ... WITH DELIMITER '|' (i.e. text mode, not CSV mode)
> > then the \| is accepted as being a literal | and the unescaped | is
> > treated as a delimiter. What is the point of the substitutions?
>
> ...
> I will provide tomorrow the exact input line, the exact COPY command and
> the error.
It works exactly as Andrew states. My error was not caused by treating
the '|' of '\|' as DELIMITER, but by not having WITH (NULL '' ...) in the COPY cmd.
I misinterpreted the error message as not matching number of columns.
Sorry for the noise.
Thanks
matthias
--
Matthias Apitz, ✉ guru@unixarea.de, http://www.unixarea.de/ +49-176-38902045
Public GnuPG key: http://www.unixarea.de/key.pub
May, 9: Спаси́бо освободители! Thank you very much, Russian liberators!