BUG #7899: allow key word as alias in subquery but Can't reference it in outer query

"=?ISO-8859-1?B?Sm92?=" <amutu@amutu.com> writes:

xxx=# select end from (select 1 as end) t;
ERROR: syntax error at or near "end"
LINE 1: select end from (select 1 as end) t;
^

You need to double-quote the outer use of "end", viz

regression=# select "end" from (select 1 as end) t;
end
-----
1
(1 row)

In the context with "as", Postgres can tell the word is meant as a
column identifier not a keyword, but there's no way for it to know that
in the outer usage.

I think use key word as alias should get a error message such as $key_word
is Key Word,should not be used as identifier bla bla,so for some complex
query error user can save a lot of time.

Well, yours is the first complaint we've ever had in that direction,
whereas we used to get a lot of complaints in the opposite direction,
back when we didn't allow keywords to be used for column names.
So I doubt we'll change it. It is an interesting gotcha though :-(

regards, tom lane

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I have get the description of this behaviour from doc 7.3.2
http://www.postgresql.org/docs/devel/static/queries-select-lists.html#QUERIES-COLUMN-LABELS
.

from the error message now,I think syntax error may emmit by the
parser,parser error make it hard to get the really condition such as the
second token ‘end’ is a select item from a select statement.

thanks

2013/2/22 Tom Lane <tgl@sss.pgh.pa.us>

"=?ISO-8859-1?B?Sm92?=" <amutu@amutu.com> writes:

xxx=# select end from (select 1 as end) t;
ERROR: syntax error at or near "end"
LINE 1: select end from (select 1 as end) t;
^

You need to double-quote the outer use of "end", viz

regression=# select "end" from (select 1 as end) t;
end
-----
1
(1 row)

In the context with "as", Postgres can tell the word is meant as a
column identifier not a keyword, but there's no way for it to know that
in the outer usage.

I think use key word as alias should get a error message such as

$key_word

is Key Word,should not be used as identifier bla bla,so for some complex
query error user can save a lot of time.

Well, yours is the first complaint we've ever had in that direction,
whereas we used to get a lot of complaints in the opposite direction,
back when we didn't allow keywords to be used for column names.
So I doubt we'll change it. It is an interesting gotcha though :-(

regards, tom lane
.

--
Jov
blog: http:amutu.com/blog <http://amutu.com/blog&gt;

can we make a cross reference from doc 4.4.1(
http://www.postgresql.org/docs/devel/static/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS
)
to
doc 7.3.2 (
http://www.postgresql.org/docs/devel/static/queries-select-lists.html#QUERIES-COLUMN-LABELS
)
*to mention that “AS” can make a key word to be a identifier?*
I have read the doc 4.4.1 and can't find this info from there so I thin it
is a bug.

2013/2/22 Jov <amutu@amutu.com>

I have get the description of this behaviour from doc 7.3.2

http://www.postgresql.org/docs/devel/static/queries-select-lists.html#QUERIES-COLUMN-LABELS
.

from the error message now,I think syntax error may emmit by the
parser,parser error make it hard to get the really condition such as the
second token ‘end’ is a select item from a select statement.

thanks

2013/2/22 Tom Lane <tgl@sss.pgh.pa.us>

"=?ISO-8859-1?B?Sm92?=" <amutu@amutu.com> writes:

xxx=# select end from (select 1 as end) t;
ERROR: syntax error at or near "end"
LINE 1: select end from (select 1 as end) t;
^

You need to double-quote the outer use of "end", viz

regression=# select "end" from (select 1 as end) t;
end
-----
1
(1 row)

In the context with "as", Postgres can tell the word is meant as a
column identifier not a keyword, but there's no way for it to know that
in the outer usage.

I think use key word as alias should get a error message such as

$key_word

is Key Word,should not be used as identifier bla bla,so for some complex
query error user can save a lot of time.

Well, yours is the first complaint we've ever had in that direction,
whereas we used to get a lot of complaints in the opposite direction,
back when we didn't allow keywords to be used for column names.
So I doubt we'll change it. It is an interesting gotcha though :-(

regards, tom lane
.

--
Jov
blog: http:amutu.com/blog <http://amutu.com/blog&gt;

--
Jov
blog: http:amutu.com/blog <http://amutu.com/blog&gt;