Re: [GENERAL] noobie question
On Thu, Jan 24, 2013 at 12:03 PM, Steve Clark scl...@netwolves.com wrote: On 01/24/2013 01:06 PM, Chris Angelico wrote: On Fri, Jan 25, 2013 at 4:45 AM, Steve Clark scl...@netwolves.com wrote: Thanks All, This is for a few very small tables, less 100 records each, that a user can delete and insert records into based on the id which is displayed in a php generated html screen. The tables are rarely updated and when they are updated only one person is accessing them at a time. I have seen several answers on inserting what about deleting? Deleting works exactly the same way; you just subtract instead of adding. And thanks Jeff, I forgot about that requirement. Still, searched update is the easiest solution. However, do seriously rethink your design. At very least, the id field is misnamed; it's not the record's identity if it changes. If your only two operations are insert and delete (with inserts permitted at either end of the list as well as in the middle), one way you could do it is to have a serially-numbered ID, and a 'pos'. Adding to the end means inserting a row with a pos one higher than the current highest. Inserting a record before another one means inserting a row with the same pos - no renumbering needed. Deleting a row is done by its id, not its position. And when you query the table, just ask for them ORDER BY POS, ID DESC - this will show them in the right order. This doesn't, however, handle arbitrary reordering of records. For that, you will ultimately need to renumber the positions. ChrisA Hi Chris, It is really called rule_num and relates to in what order firewall rules are applied. And it used to allow the user to place the firewall rules where they want them in relation to other rules. This is an old design, of which I had no input, but am now maintaining. Like I said initially I have php, bash or C code to do the reordering and was just wondering if there was a slick way to do it without having to resort to some external mechanism. Thanks to all who responded. So do the numbers need to be a gapless sequence? if not why not have each position be, say, 10,000 apart, and just insert new ones halfway between the two nearest rules? -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] noobie question
On 01/24/2013 08:47 AM, Steve Clark wrote: Hi list, This may be really simple - I usually do it using a procedural language such as php or a bash script. Say I have a table that has 2 columns like create table foo ( id integer not null, name text ); CREATE UNIQUE INDEX foo_pkey on foo using btree ( id int4_ops ); with 10 rows of data where id is 1 to 10. Now I want to insert a new row ahead of id 5 so I have to renumber the rows from 5 to 10 increasing each by one. Or the opposite I want to delete a row an renumber to close up the gap. Is there an easy way to do this in postgresql without resulting to some external language? I can see this taking a lot of overhead as the table increases. I guess it comes down to what you are trying to achieve? Do you want a gapless sequence? Do you want a ROWNUM? Something else? Thanks for your consideration. -- Adrian Klaver adrian.kla...@gmail.com -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] noobie question
On Thu, Jan 24, 2013 at 8:53 AM, Chris Angelico ros...@gmail.com wrote: On Fri, Jan 25, 2013 at 3:47 AM, Steve Clark scl...@netwolves.com wrote: Say I have a table that has 2 columns like create table foo ( id integer not null, name text ); CREATE UNIQUE INDEX foo_pkey on foo using btree ( id int4_ops ); with 10 rows of data where id is 1 to 10. Now I want to insert a new row ahead of id 5 so I have to renumber the rows from 5 to 10 increasing each by one. Or the opposite I want to delete a row an renumber to close up the gap. Is there an easy way to do this in postgresql without resulting to some external language? This is sounding, not like an ID, but like a position marker or something. It's most certainly possible; all you need is a searched update: UPDATE foo SET id=id+1 WHERE id=5; INSERT INTO foo VALUES (5,'new item at pos 5'); To do this reliably, you would have to set the unique constraint to DEFERRABLE INITIALLY DEFERRED, otherwise you will get errors due to transient duplicates. If his design requires that this kind of update be done regularly, he should probably reconsider that design. Cheers, Jeff -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] noobie question
On 01/24/2013 12:36 PM, Jeff Janes wrote: On Thu, Jan 24, 2013 at 8:53 AM, Chris Angelico ros...@gmail.com wrote: On Fri, Jan 25, 2013 at 3:47 AM, Steve Clark scl...@netwolves.com wrote: Say I have a table that has 2 columns like create table foo ( id integer not null, name text ); CREATE UNIQUE INDEX foo_pkey on foo using btree ( id int4_ops ); with 10 rows of data where id is 1 to 10. Now I want to insert a new row ahead of id 5 so I have to renumber the rows from 5 to 10 increasing each by one. Or the opposite I want to delete a row an renumber to close up the gap. Is there an easy way to do this in postgresql without resulting to some external language? This is sounding, not like an ID, but like a position marker or something. It's most certainly possible; all you need is a searched update: UPDATE foo SET id=id+1 WHERE id=5; INSERT INTO foo VALUES (5,'new item at pos 5'); To do this reliably, you would have to set the unique constraint to DEFERRABLE INITIALLY DEFERRED, otherwise you will get errors due to transient duplicates. If his design requires that this kind of update be done regularly, he should probably reconsider that design. Cheers, Jeff Thanks All, This is for a few very small tables, less 100 records each, that a user can delete and insert records into based on the id which is displayed in a php generated html screen. The tables are rarely updated and when they are updated only one person is accessing them at a time. I have seen several answers on inserting what about deleting? -- Stephen Clark -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] noobie question
-Original Message- From: pgsql-general-ow...@postgresql.org [mailto:pgsql-general-ow...@postgresql.org] On Behalf Of Steve Clark Sent: Thursday, January 24, 2013 12:46 PM To: Jeff Janes Cc: Chris Angelico; pgsql-general@postgresql.org Subject: Re: [GENERAL] noobie question On 01/24/2013 12:36 PM, Jeff Janes wrote: On Thu, Jan 24, 2013 at 8:53 AM, Chris Angelico ros...@gmail.com wrote: On Fri, Jan 25, 2013 at 3:47 AM, Steve Clark scl...@netwolves.com wrote: Say I have a table that has 2 columns like create table foo ( id integer not null, name text ); CREATE UNIQUE INDEX foo_pkey on foo using btree ( id int4_ops ); with 10 rows of data where id is 1 to 10. Now I want to insert a new row ahead of id 5 so I have to renumber the rows from 5 to 10 increasing each by one. Or the opposite I want to delete a row an renumber to close up the gap. Is there an easy way to do this in postgresql without resulting to some external language? This is sounding, not like an ID, but like a position marker or something. It's most certainly possible; all you need is a searched update: UPDATE foo SET id=id+1 WHERE id=5; INSERT INTO foo VALUES (5,'new item at pos 5'); To do this reliably, you would have to set the unique constraint to DEFERRABLE INITIALLY DEFERRED, otherwise you will get errors due to transient duplicates. If his design requires that this kind of update be done regularly, he should probably reconsider that design. Cheers, Jeff Thanks All, This is for a few very small tables, less 100 records each, that a user can delete and insert records into based on the id which is displayed in a php generated html screen. The tables are rarely updated and when they are updated only one person is accessing them at a time. I have seen several answers on inserting what about deleting? -- Stephen Clark -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general --- delete from mytable where id = 4; update mytable set id = id-1 where id 4; -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] noobie question
On Fri, Jan 25, 2013 at 4:45 AM, Steve Clark scl...@netwolves.com wrote: Thanks All, This is for a few very small tables, less 100 records each, that a user can delete and insert records into based on the id which is displayed in a php generated html screen. The tables are rarely updated and when they are updated only one person is accessing them at a time. I have seen several answers on inserting what about deleting? Deleting works exactly the same way; you just subtract instead of adding. And thanks Jeff, I forgot about that requirement. Still, searched update is the easiest solution. However, do seriously rethink your design. At very least, the id field is misnamed; it's not the record's identity if it changes. If your only two operations are insert and delete (with inserts permitted at either end of the list as well as in the middle), one way you could do it is to have a serially-numbered ID, and a 'pos'. Adding to the end means inserting a row with a pos one higher than the current highest. Inserting a record before another one means inserting a row with the same pos - no renumbering needed. Deleting a row is done by its id, not its position. And when you query the table, just ask for them ORDER BY POS, ID DESC - this will show them in the right order. This doesn't, however, handle arbitrary reordering of records. For that, you will ultimately need to renumber the positions. ChrisA -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] noobie question
On 01/24/2013 01:06 PM, Chris Angelico wrote: On Fri, Jan 25, 2013 at 4:45 AM, Steve Clark scl...@netwolves.com wrote: Thanks All, This is for a few very small tables, less 100 records each, that a user can delete and insert records into based on the id which is displayed in a php generated html screen. The tables are rarely updated and when they are updated only one person is accessing them at a time. I have seen several answers on inserting what about deleting? Deleting works exactly the same way; you just subtract instead of adding. And thanks Jeff, I forgot about that requirement. Still, searched update is the easiest solution. However, do seriously rethink your design. At very least, the id field is misnamed; it's not the record's identity if it changes. If your only two operations are insert and delete (with inserts permitted at either end of the list as well as in the middle), one way you could do it is to have a serially-numbered ID, and a 'pos'. Adding to the end means inserting a row with a pos one higher than the current highest. Inserting a record before another one means inserting a row with the same pos - no renumbering needed. Deleting a row is done by its id, not its position. And when you query the table, just ask for them ORDER BY POS, ID DESC - this will show them in the right order. This doesn't, however, handle arbitrary reordering of records. For that, you will ultimately need to renumber the positions. ChrisA Hi Chris, It is really called rule_num and relates to in what order firewall rules are applied. And it used to allow the user to place the firewall rules where they want them in relation to other rules. This is an old design, of which I had no input, but am now maintaining. Like I said initially I have php, bash or C code to do the reordering and was just wondering if there was a slick way to do it without having to resort to some external mechanism. Thanks to all who responded. -- Stephen Clark -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] noobie question
On Thu, Jan 24, 2013 at 14:03:33 -0500, Steve Clark scl...@netwolves.com wrote: It is really called rule_num and relates to in what order firewall rules are applied. And it used to allow the user to place the firewall rules where they want them in relation to other rules. If you just need ordering, you could choose to use a string or numeric to give you ordering. That allows you to insert values in between existing records without having to renumber. When displaying the data the application can number them based on ordering. And keep track of the current mapping between the number on the screen and the key in the database. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
