Обсуждение: 'value' has special behaviour in alter system
The following documentation comment has been logged on the website: Page: https://www.postgresql.org/docs/15/sql-altersystem.html Description: Documentation say ALTER SYSTEM SET configuration_parameter { TO | = } { value | 'value' | DEFAULT } The variant 'value' has special, not obvious behaviour and must be documented. For instance ALTER SYSTEM SET shared_preload_libraries TO a, b, c; Lead to shared_preload_libraries = 'a, b, c' in the postgresql.auto.conf and working fine. (If a, b, c are correct libraries.) But ALTER SYSTEM SET shared_preload_libraries TO 'a, b, c'; Lead to shared_preload_libraries = '"a, b, c"' in the postgresql.auto.conf and postgresql will not even start. Without any errors in the postgresql log files. :) In the system log will be "file not found".
On Thu, Dec 15, 2022 at 4:45 AM PG Doc comments form <noreply@postgresql.org> wrote:
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/15/sql-altersystem.html
Description:
Documentation say
ALTER SYSTEM SET configuration_parameter { TO | = } { value | 'value' |
DEFAULT }
The variant 'value' has special, not obvious behaviour and must be
documented.
This syntax representation and accompanying text annoys me too. It is logical behavior and described accurately, but I think readability could be improved.
I suggest changing it to:
SET configuration_parameter { TO | = } { value [, ...] | DEFAULT }
Values can be specified as unquoted alphanumeric+underscore sequences. If the value contains any non-alphanumeric (plus underscore) characters it should be enclosed in quotes (single or double, it does not matter). For settings that accept multiple values, separate each value to be supplied with a comma (and optional whitespace).
This concern is not limited to this page though, and should be applied elsewhere as is applicable.
I haven't tried to exhaustively enumerate when quoting is required, and probably the quoting rules should be centralized and the description simplified to:
The rules for when individual values must be quoted is described in Chapter 20.1.1. For settings that accept multiple values, separate each value with a comma and optional whitespace.
That chapter does indeed already explain for each type of value when quoting is required.
David J.
On 12/15/22 10:50 AM, David G. Johnston wrote: > On Thu, Dec 15, 2022 at 4:45 AM PG Doc comments form > <noreply@postgresql.org <mailto:noreply@postgresql.org>> wrote: > > The following documentation comment has been logged on the website: > > Page: https://www.postgresql.org/docs/15/sql-altersystem.html > <https://www.postgresql.org/docs/15/sql-altersystem.html> > Description: > > Documentation say > ALTER SYSTEM SET configuration_parameter { TO | = } { value | 'value' | > DEFAULT } > > The variant 'value' has special, not obvious behaviour and must be > documented. > > > This syntax representation and accompanying text annoys me too. It is > logical behavior and described accurately, but I think readability could > be improved. > > I suggest changing it to: > > SET configuration_parameter { TO | = } { value [, ...] | DEFAULT } > > Values can be specified as unquoted alphanumeric+underscore sequences. > If the value contains any non-alphanumeric (plus underscore) characters > it should be enclosed in quotes (single or double, it does not matter). > For settings that accept multiple values, separate each value to be > supplied with a comma (and optional whitespace). +1 in general. I would also suggest we add an example in the Examples section to show what the output is when you add single-quotes. Jonathan
Вложения
"Jonathan S. Katz" <jkatz@postgresql.org> writes:
> On 12/15/22 10:50 AM, David G. Johnston wrote:
>> I suggest changing it to:
>> SET configuration_parameter { TO | = } { value [, ...] | DEFAULT }
> +1 in general. I would also suggest we add an example in the Examples
> section to show what the output is when you add single-quotes.
I think the core problem here is that the syntax diagram and discussion
don't clearly discuss the behavior for list values. David's version of
the syntax diagram looks fine, but not sure about the text. There likely
needs to be some explicit acknowledgement of the fact that some GUCs
act differently than others (cf GUC_LIST_INPUT and GUC_LIST_QUOTE flags).
+1 for examples, for sure.
regards, tom lane
On Thu, Dec 15, 2022 at 12:10:27PM -0500, Tom Lane wrote:
> "Jonathan S. Katz" <jkatz@postgresql.org> writes:
> > On 12/15/22 10:50 AM, David G. Johnston wrote:
> >> I suggest changing it to:
> >> SET configuration_parameter { TO | = } { value [, ...] | DEFAULT }
>
> > +1 in general. I would also suggest we add an example in the Examples
> > section to show what the output is when you add single-quotes.
>
> I think the core problem here is that the syntax diagram and discussion
> don't clearly discuss the behavior for list values. David's version of
> the syntax diagram looks fine, but not sure about the text. There likely
> needs to be some explicit acknowledgement of the fact that some GUCs
> act differently than others (cf GUC_LIST_INPUT and GUC_LIST_QUOTE flags).
>
> +1 for examples, for sure.
Finally getting back to this, there is a lot going on and Tom is right
that the inconsistent use of GUC_LIST_QUOTE adds a lot of confusion.
Here are the list settings, and which ones add double-quotes to
non-alphanumeric quoted values:
GUC_LIST_QUOTE (adds quotes)
temp_tablespaces
session_preload_libraries
shared_preload_libraries
local_preload_libraries
search_path
unix_socket_directories
NO GUC_LIST_QUOTE (does not add quotes)
DateStyle
createrole_self_grant
log_destination
listen_addresses
synchronous_standby_names
wal_consistency_checking
debug_io_direct
and this leads to different quoting behaviors depending on which
category of list you are using. First, let's look at alphanumeric
values, which are treated the same by list types with different
GUC_LIST_QUOTE statuses:
ALTER SYSTEM SET shared_preload_libraries TO a, b, c;
.conf shared_preload_libraries = 'a, b, c'
ALTER SYSTEM SET listen_addresses TO a, b, c;
.conf listen_addresses = 'a, b, c'
Even with quotes, the output is the same:
ALTER SYSTEM SET shared_preload_libraries TO a, 'b', c;
.conf shared_preload_libraries = 'a, b, c'
ALTER SYSTEM SET shared_preload_libraries TO a, "b", c;
.conf shared_preload_libraries = 'a, b, c'
ALTER SYSTEM SET listen_addresses TO a, 'b', c;
.conf listen_addresses = 'a, b, c'
ALTER SYSTEM SET listen_addresses TO a, "b", c;
.conf listen_addresses = 'a, b, c'
With non-alphanumeric (spaces), there is a difference:
ALTER SYSTEM SET shared_preload_libraries TO a, 'b x', c;
.conf shared_preload_libraries = 'a, "b x", c'
ALTER SYSTEM SET listen_addresses TO a, 'b x', c;
.conf listen_addresses = 'a, b x, c'
For listen_addresses to get the quoting behavior of
shared_preload_libraries, I have to use double-quotes inside single
quotes:
ALTER SYSTEM SET listen_addresses TO 'a, "b x", c';
.conf listen_addresses = 'a, "b x", c'
Do we want to retain this difference in list processing?
I have developed the attached patch to document this.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EDB https://enterprisedb.com
Only you can decide what is important to you.
Вложения
Bruce Momjian <bruce@momjian.us> writes:
> I have developed the attached patch to document this.
This seems a little imprecise:
+ Values with non-alphanumeric characters must be quoted.
I think accurate is more like "Values that are neither a number
nor a valid identifier must be quoted."
Also, that para already mentions that the input can be a
comma-separated list when appropriate, so your add-on para seems
partially repetitive. I think you could just drop the first
sentence of it.
regards, tom lane
On Tue, Oct 24, 2023 at 02:05:53PM -0400, Tom Lane wrote: > Bruce Momjian <bruce@momjian.us> writes: > > I have developed the attached patch to document this. > > This seems a little imprecise: > > + Values with non-alphanumeric characters must be quoted. > > I think accurate is more like "Values that are neither a number > nor a valid identifier must be quoted." > > Also, that para already mentions that the input can be a > comma-separated list when appropriate, so your add-on para seems > partially repetitive. I think you could just drop the first > sentence of it. Agreed, updated patch attached. -- Bruce Momjian <bruce@momjian.us> https://momjian.us EDB https://enterprisedb.com Only you can decide what is important to you.
Вложения
On Tue, Oct 24, 2023 at 02:36:14PM -0400, Bruce Momjian wrote: > On Tue, Oct 24, 2023 at 02:05:53PM -0400, Tom Lane wrote: > > Bruce Momjian <bruce@momjian.us> writes: > > > I have developed the attached patch to document this. > > > > This seems a little imprecise: > > > > + Values with non-alphanumeric characters must be quoted. > > > > I think accurate is more like "Values that are neither a number > > nor a valid identifier must be quoted." > > > > Also, that para already mentions that the input can be a > > comma-separated list when appropriate, so your add-on para seems > > partially repetitive. I think you could just drop the first > > sentence of it. > > Agreed, updated patch attached. Patch applied to all supported versions. -- Bruce Momjian <bruce@momjian.us> https://momjian.us EDB https://enterprisedb.com Only you can decide what is important to you.