Thread: Limit on multi-field indexes?
Am I correct in believing that there is a limit of seven columns in a multi-filed index? If so, is it possible to increase this limit (to at least eight) ? Cheers and thanks, Stephen. ======================================================================== Stephen Davies Consulting scldad@sdc.com.au Adelaide, South Australia. Voice: 61-8-82728863 Computing & Network solutions. Fax: 61-8-82741015
> Am I correct in believing that there is a limit of seven columns in a > multi-filed index? > > If so, is it possible to increase this limit (to at least eight) ? > > Cheers and thanks, Not easily. The columns are stored in an int28 column, that holds 8 two-byte integer. We would have to change that to a larger field. Very few people have asked for this. -- Bruce Momjian | 830 Blythe Avenue maillist@candle.pha.pa.us | Drexel Hill, Pennsylvania 19026 http://www.op.net/~candle | (610) 353-9879(w) + If your life is a hard drive, | (610) 853-3000(h) + Christ can be your backup. |
> > Am I correct in believing that there is a limit of seven columns in a > > multi-filed index? > > > > If so, is it possible to increase this limit (to at least eight) ? > > > > Cheers and thanks, > > Not easily. The columns are stored in an int28 column, that holds 8 > two-byte integer. We would have to change that to a larger field. Very > few people have asked for this. > Getting desperate here. If it holds 8 integers, why can't I have 8 columns in a multi-field index? I am currently writing a tool to replicate any database to a PostgreSQL mirror and the very first customer for this tool has several tables with 8 fields in their primary key. Sod's Law:-(( Cheers and thanks, Stephen. ======================================================================== Stephen Davies Consulting scldad@sdc.com.au Adelaide, South Australia. Voice: 61-8-82728863 Computing & Network solutions. Fax: 61-8-82741015
What do I use to read postgres's log, pg_log??? Please reply to my email if possible. Thanks -jeremy
Thus spake Stephen Davies
> I am currently writing a tool to replicate any database to a PostgreSQL mirror
> and the very first customer for this tool has several tables with 8 fields in
> their primary key. Sod's Law:-((
Could that database be badly in need of a redesign? :-)
--
D'Arcy J.M. Cain <darcy@{druid|vex}.net> | Democracy is three wolves
http://www.druid.net/darcy/ | and a sheep voting on
+1 416 424 2871 (DoD#0082) (eNTP) | what's for dinner.
> > > Am I correct in believing that there is a limit of seven columns in a > > > multi-filed index? > > > > > > If so, is it possible to increase this limit (to at least eight) ? > > > > > > Cheers and thanks, > > > > Not easily. The columns are stored in an int28 column, that holds 8 > > two-byte integer. We would have to change that to a larger field. Very > > few people have asked for this. > > > Getting desperate here. > > If it holds 8 integers, why can't I have 8 columns in a multi-field index? > > I am currently writing a tool to replicate any database to a PostgreSQL mirror > and the very first customer for this tool has several tables with 8 fields in > their primary key. Sod's Law:-(( There is no field in pg_index to determine the number of fields in the index, so it scans pg_index.indkey until it hits a 0. Now, I suppose we could change the code so it goes through indkey until it gets a 0, or reaches the eighth entry. -- Bruce Momjian | 830 Blythe Avenue maillist@candle.pha.pa.us | Drexel Hill, Pennsylvania 19026 http://www.op.net/~candle | (610) 353-9879(w) + If your life is a hard drive, | (610) 853-3000(h) + Christ can be your backup. |
> If it holds 8 integers, why can't I have 8 columns in a multi-field index? > > I am currently writing a tool to replicate any database to a PostgreSQL mirror > and the very first customer for this tool has several tables with 8 fields in > their primary key. Sod's Law:-(( OK, I am committing changes which will allow 8-key indexes, rather than just seven. Please test this at your convenience. -- Bruce Momjian | 830 Blythe Avenue maillist@candle.pha.pa.us | Drexel Hill, Pennsylvania 19026 http://www.op.net/~candle | (610) 353-9879(w) + If your life is a hard drive, | (610) 853-3000(h) + Christ can be your backup. |
> > If it holds 8 integers, why can't I have 8 columns in a multi-field index? > > > > I am currently writing a tool to replicate any database to a PostgreSQL mirror > > and the very first customer for this tool has several tables with 8 fields in > > their primary key. Sod's Law:-(( > > OK, I am committing changes which will allow 8-key indexes, rather than > just seven. Please test this at your convenience. > Good on ya Bruce!! (Traditional Aussie saying ;-) ) Thank you very much. Where might I find the patch? Cheers and thanks, Stephen. ======================================================================== Stephen Davies Consulting scldad@sdc.com.au Adelaide, South Australia. Voice: 61-8-82728863 Computing & Network solutions. Fax: 61-8-82741015
> > > If it holds 8 integers, why can't I have 8 columns in a multi-field index? > > > > > > I am currently writing a tool to replicate any database to a PostgreSQL mirror > > > and the very first customer for this tool has several tables with 8 fields in > > > their primary key. Sod's Law:-(( > > > > OK, I am committing changes which will allow 8-key indexes, rather than > > just seven. Please test this at your convenience. > > > > Good on ya Bruce!! > > (Traditional Aussie saying ;-) ) > > Thank you very much. Where might I find the patch? You have to get involved in the 6.4 beta by joining the hackers list, and/or get a snapshot from the ftp site that has a date after today's date. -- Bruce Momjian | 830 Blythe Avenue maillist@candle.pha.pa.us | Drexel Hill, Pennsylvania 19026 http://www.op.net/~candle | (610) 353-9879(w) + If your life is a hard drive, | (610) 853-3000(h) + Christ can be your backup. |