Обсуждение: [HACKERS] proposal: psql statements \gstore \gstore_binary (instead COPY RAW)

On Dec 9, 2016 18:40, "Pavel Stehule" <pavel.stehule@gmail.com> wrote:

Hi

Long time I am pushing a COPY RAW - without success.

Now I propose functionally similar solution - reduced to only to psql console

Now we have a statement \g for execution query, \gset for exec and store result in memory and I propose \gstore for storing result in file and \gstore_binary for storing result in file with binary passing. The query result should be one row, one column.

Usage:

SELECT image FROM accounts WHERE id = xxx

\gstore_binary ~/image.png

What do you think about this proposal?

I might be missing something, but is it different from:

\t

\a

\o output_filename

SELECT ...

\o

?

--

Alex

On 12/9/16 9:39 AM, Pavel Stehule wrote:

SELECT image FROM accounts WHERE id = xxx
\gstore_binary ~/image.png

What do you think about this proposal?

Seems reasonable.

I've lost track at this point... is there a way to go the other direction with that as well? Namely, stick the contents of a file into a field via an INSERT or UPDATE?

I've done that in the past via psql -v var=`cat file`, but there's obviously some significant drawbacks to that...
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
855-TREBLE2 (855-873-2532)

2016-12-10 2:27 GMT+01:00 Jim Nasby <Jim.Nasby@bluetreble.com>:

On 12/9/16 9:39 AM, Pavel Stehule wrote:

SELECT image FROM accounts WHERE id = xxx
\gstore_binary ~/image.png

What do you think about this proposal?

Seems reasonable.

I've lost track at this point... is there a way to go the other direction with that as well? Namely, stick the contents of a file into a field via an INSERT or UPDATE?

a target of this feature is storing only. For import there should be another statements.

I am think so there is a consensus (with Tom) on binary passing mode. Some like

\set USE_BINARY on

What is not clean (where is not a agreement is a way how to get a some content) - if we use a variables with content (not references), then we can or cannot to have special statement

so some ways how to push some binary content to server

A)

\set xxxx `cat file`

\set USE_BINARY on

INSERT INTO tab(id, data) VALUES(1, :xxxx::bytea);

B)

\set xxxx `cat file`

INSERT INTO tab(id, data) VALUES (1, :x'xxxx'); -- use bytea escape

C)

\load_binary xxxx file

INSERT INTO tab(id, data) VALUES(1, :'xxxx');

D)

\load xxxx file

\set USE_BINARY on

INSERT INTO tab(id, data) VALUES(1, :xxxx::bytea);

E)

\set xxxx ``cat file``

INSERT INTO tab(id, data) VALUES (1, :'xxxx');

any from mentioned variants has some advantages - and I don't see a clean winner. I like a binary mode for passing - the patch is small and clean and possible errors are well readable (not a MBytes of hexa numbers). Passing in text mode is safe - although the some errors, logs can be crazy. I would to use some form of "load" backslash command ("load", "load_binary"): a) we can implement a file tab complete, b) we can hide some platform specific ("cat" linux, "type" windows).

Now, only text variables are supported - it is enough for passing XML, JSON - but not for binary data (one important variant is passing XML binary for automatic XML internal encoding transformation). So we should to encode content before storing to variable, or we should to introduce binary variables. It is not hard - introduce new functions, current API will supports text variables.

The implementation of these variants is short, simple - we can implement more than exactly one way - @E is general, but little bit magic, and without a autocomplete possibility, @C is very clear

The discussion can be about importance following features:

1. binary passing  (important for XML, doesn't fill a logs, a speed is not important in this context)

2. tab complete support

3. verbosity, readability

I would to know how these points are important, interesting for other people? It can helps with choosing variant or variants that we can implement. I don't expect some significant differences in implementation complexity of mentioned variants - the code changes will be +/- same.

Regards

Pavel

 

I've done that in the past via psql -v var=`cat file`, but there's obviously some significant drawbacks to that...
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
855-TREBLE2 (855-873-2532)

Hi

2016-12-09 18:39 GMT+01:00 Pavel Stehule <pavel.stehule@gmail.com>:

Hi

Long time I am pushing a COPY RAW - without success.

Now I propose functionally similar solution - reduced to only to psql console

Now we have a statement \g for execution query, \gset for exec and store result in memory and I propose \gstore for storing result in file and \gstore_binary for storing result in file with binary passing. The query result should be one row, one column.

Usage:

SELECT image FROM accounts WHERE id = xxx

\gstore_binary ~/image.png

What do you think about this proposal?

here is a poc patch

Regards

Pavel

Usage:

postgres=# set client_encoding to 'latin2';
SET
Time: 1,561 ms
postgres=# select a from foo
postgres-# \gbstore ~/doc.xml
Time: 1,749 ms

content of doc.xml
<?xml version="1.0" encoding="LATIN2"?><a>příliš žluťoučký kůň se napil žluté vody</a>

Regards

Pavel