Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[]
OK, what is the TODO item text? --- Joe Conway wrote: Bruce Momjian wrote: Is this a TODO item? Probably. I posted some questions regarding whether or not to break backward compatiblity, and received no replies. In the meanwhile, I've been doing a major system integration in Korea for the last 2 weeks, and won't get back to home, or to anything like a reasonably normal schedule until after July 2. I doubt I'll have time to do much between now and feature freeze. Joe ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED] -- Bruce Momjian| http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup.| Newtown Square, Pennsylvania 19073 ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[]
Bruce Momjian wrote: Is this a TODO item? Probably. I posted some questions regarding whether or not to break backward compatiblity, and received no replies. In the meanwhile, I've been doing a major system integration in Korea for the last 2 weeks, and won't get back to home, or to anything like a reasonably normal schedule until after July 2. I doubt I'll have time to do much between now and feature freeze. Joe ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[]
Is this a TODO item? --- Markus Bertheau ? wrote: ? ???, 06/06/2005 ? 08:58 -0700, Joe Conway ?: Joe Conway wrote: Actually, consistent with my last post, I think array_upper() on a zero-element array should return NULL. A zero-element array has a defined lower bound, but its upper bound is not zero -- it is really undefined. Just to clarify my response, this is what I propose: regression=# select array_upper('[2][1:]={{},{}}'::int[],1); array_upper - 2 (1 row) regression=# select array_upper('[2][1:]={{},{}}'::int[],2) IS NULL; ?column? -- t (1 row) Hmm, this gets really complicated and inconsistent. Complicated means unusable. What about modifying the dimension syntax such that the second number means number of elements instead of upper bound? That particular problem would go away then, and array_upper('[0:0]={}'::int[]) can return the correct 0 then. What I'm actually worrying about is that array_upper(array(select 1 where false)) returns 0. An option would be to drop the possibility to let the array start at another index than 0. I don't know why it was decided to do that in the first place. It seems a rather odd feature to me. Markus -- Markus Bertheau ? [EMAIL PROTECTED] ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly -- Bruce Momjian| http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup.| Newtown Square, Pennsylvania 19073 ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[] resp. {}
, 24/05/2005 00:06 -0400, Tom Lane : Joe Conway [EMAIL PROTECTED] writes: Markus Bertheau wrote: why does SELECT ARRAY(SELECT 1 WHERE FALSE) return NULL instead of ARRAY[] resp. '{}'? Why would you expect an empty array instead of a NULL? I think he's got a good point, actually. We document the ARRAY-with- parens-around-a-SELECT syntax as The resulting one-dimensional array will have an element for each row in the subquery result, with an element type matching that of the subquery's output column. To me, that implies that a subquery result of no rows generates a one-dimensional array of no elements, not a null array. By analogy, array_upper('{}'::TEXT[], 1) should return 0 instead of NULL. Markus -- Markus Bertheau [EMAIL PROTECTED] ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[] resp. {}
, 06/06/2005 10:44 -0400, Tom Lane : Markus Bertheau =?UTF-8?Q?=E2=98=AD?= [EMAIL PROTECTED] writes: By analogy, array_upper('{}'::TEXT[], 1) should return 0 instead of NULL. No, that doesn't follow ... we've traditionally considered '{}' to denote a zero-dimensional array. But array_upper(ARRAY(SELECT 1 WHERE FALSE), 1) should return 0, and array_upper(ARRAY[], 1), when the ARRAY[] syntax is supported, should return 0. Do I get that right? Markus -- Markus Bertheau [EMAIL PROTECTED] ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[] resp. {}
Markus Bertheau =?UTF-8?Q?=E2=98=AD?= [EMAIL PROTECTED] writes: By analogy, array_upper('{}'::TEXT[], 1) should return 0 instead of NULL. No, that doesn't follow ... we've traditionally considered '{}' to denote a zero-dimensional array. A 1-D array of no elements is '[1:0]={}', just as Joe shows ... or at least it would be except for an overenthusiastic error check: regression=# select '[1:0]={}' :: int[]; ERROR: upper bound cannot be less than lower bound I think this should be a legal boundary case. In general, it should be possible to form zero-size arrays of any number of dimensions. regards, tom lane ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[] resp. {}
Tom Lane wrote: Markus Bertheau =?UTF-8?Q?=E2=98=AD?= [EMAIL PROTECTED] writes: By analogy, array_upper('{}'::TEXT[], 1) should return 0 instead of NULL. No, that doesn't follow ... we've traditionally considered '{}' to denote a zero-dimensional array. A 1-D array of no elements is '[1:0]={}', just as Joe shows ... or at least it would be except for an overenthusiastic error check: regression=# select '[1:0]={}' :: int[]; ERROR: upper bound cannot be less than lower bound I think this should be a legal boundary case. In general, it should be possible to form zero-size arrays of any number of dimensions. I've been playing with exactly this over the weekend. Of course, as usual, the devil is in the details. For instance, using the above notation, how would I specify a zero-element 1D array starting at a lower bound index of 0? The answer following the above pattern would be: select '[0:-1]={}'::int[]; You could not use '[0:0]={}'::int[], because that would be a one-element array. I propose the following instead: regression=# select '[1:]={}' :: int[]; int4 -- {} (1 row) regression=# select array_dims('[1:]={}' :: int[]); array_dims [1:] (1 row) In other words, an missing upper bound indicates zero elements. Now the next question; what does a 2D zero-element array look like? I think this makes sense: regression=# select '[1:2][1:]={{},{}}'::int[]; int4 -- {} (1 row) Except (I think) array_out() should probably output something closer to the input literal. Any thoughts on this? Joe ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[] resp. {}
Markus Bertheau wrote: , 06/06/2005 10:44 -0400, Tom Lane : Markus Bertheau =?UTF-8?Q?=E2=98=AD?= [EMAIL PROTECTED] writes: By analogy, array_upper('{}'::TEXT[], 1) should return 0 instead of NULL. No, that doesn't follow ... we've traditionally considered '{}' to denote a zero-dimensional array. But array_upper(ARRAY(SELECT 1 WHERE FALSE), 1) should return 0, and array_upper(ARRAY[], 1), when the ARRAY[] syntax is supported, should return 0. Actually, consistent with my last post, I think array_upper() on a zero-element array should return NULL. A zero-element array has a defined lower bound, but its upper bound is not zero -- it is really undefined. Joe ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[] resp.
Joe Conway wrote: Actually, consistent with my last post, I think array_upper() on a zero-element array should return NULL. A zero-element array has a defined lower bound, but its upper bound is not zero -- it is really undefined. Just to clarify my response, this is what I propose: regression=# select array_upper('[2][1:]={{},{}}'::int[],1); array_upper - 2 (1 row) regression=# select array_upper('[2][1:]={{},{}}'::int[],2) IS NULL; ?column? -- t (1 row) Joe ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[]
, 06/06/2005 08:58 -0700, Joe Conway : Joe Conway wrote: Actually, consistent with my last post, I think array_upper() on a zero-element array should return NULL. A zero-element array has a defined lower bound, but its upper bound is not zero -- it is really undefined. Just to clarify my response, this is what I propose: regression=# select array_upper('[2][1:]={{},{}}'::int[],1); array_upper - 2 (1 row) regression=# select array_upper('[2][1:]={{},{}}'::int[],2) IS NULL; ?column? -- t (1 row) Hmm, this gets really complicated and inconsistent. Complicated means unusable. What about modifying the dimension syntax such that the second number means number of elements instead of upper bound? That particular problem would go away then, and array_upper('[0:0]={}'::int[]) can return the correct 0 then. What I'm actually worrying about is that array_upper(array(select 1 where false)) returns 0. An option would be to drop the possibility to let the array start at another index than 0. I don't know why it was decided to do that in the first place. It seems a rather odd feature to me. Markus -- Markus Bertheau [EMAIL PROTECTED] ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[] resp.
Markus Bertheau wrote: Hmm, this gets really complicated and inconsistent. Complicated means unusable. What about modifying the dimension syntax such that the second number means number of elements instead of upper bound? That particular problem would go away then, and array_upper('[0:0]={}'::int[]) can return the correct 0 then. What I'm actually worrying about is that array_upper(array(select 1 where false)) returns 0. An option would be to drop the possibility to let the array start at another index than 0. I don't know why it was decided to do that in the first place. It seems a rather odd feature to me. Actually I like both of these ideas, and have advocated the second one myself before. But it isn't backward compatible -- anyone else have an opinion? SQL2003 actually specifies that an array *should* start at 1: 4.10.2 Arrays An array is a collection A in which each element is associated with exactly one ordinal position in A. If n is the cardinality of A, then the ordinal position p of an element is an integer in the range 1 (one) p n. Joe ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [HACKERS] [SQL] ARRAY() returning NULL instead of ARRAY[] resp. {}
Dnia 24-05-2005, wto o godzinie 00:06 -0400, Tom Lane napisa(a): Joe Conway [EMAIL PROTECTED] writes: Markus Bertheau wrote: why does SELECT ARRAY(SELECT 1 WHERE FALSE) return NULL instead of ARRAY[] resp. '{}'? Why would you expect an empty array instead of a NULL? I think he's got a good point, actually. We document the ARRAY-with- parens-around-a-SELECT syntax as The resulting one-dimensional array will have an element for each row in the subquery result, with an element type matching that of the subquery's output column. To me, that implies that a subquery result of no rows generates a one-dimensional array of no elements, not a null array. The point Markus is complaining about seems like it should be easily fixable. Great. Does this belong on the TODO? -- Markus Bertheau [EMAIL PROTECTED] signature.asc Description: This is a digitally signed message part