Re: [HACKERS] DB Tuning Notes for comment...
At 03:54 PM 9/12/2002 -0500, Tom Lane wrote: I have some uncommitted patches concerning the FSM management heuristics from Stephen Marshall, which I deemed too late/risky for 7.3, but we should get something done for 7.4. Anyone interested in playing around in this area? I'd be interested in seeing the patches, but can't commit to doing anything with them at this point. I would like to get to the bottom of the weird behaviour, however. Philip Warner| __---_ Albatross Consulting Pty. Ltd. |/ - \ (A.B.N. 75 008 659 498) | /(@) __---_ Tel: (+61) 0500 83 82 81 | _ \ Fax: (+61) 03 5330 3172 | ___ | Http://www.rhyme.com.au |/ \| |---- PGP key available upon request, | / and from pgp5.ai.mit.edu:11371 |/ ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html
Re: [HACKERS] DB Tuning Notes for comment...
On Sun, 2002-12-08 at 09:41, Philip Warner wrote: Any comments or suggestions would be welcome. first and foremost, this is really excellent work! We need to look into getting this info into the standard documentation and/or Bruce's tuning guide. Tuning == 1. max_fsm_relations First of all, the free space manager is useless at managing free space if it can not map all relations (including system relations and toast relations). The following query should give the correct ballpark: select count(*) from pg_class where not relkind in ('i','v'); It should be noted that if you have multiple databases, you'll need to get the number of relations minus the system tables for each database, then add in the number of system tables. Set max_fsm_relations to a number greater than this. Add extra to deal with any tables you will create etc. It costs 40 bytes per table, so be generous - if it is set too low, you will get bizarre space usage. 2. VACUUM Frequency --- Ideally VACUUM should run constantly; a future version will support something like it. But for now, vacuum should be run when a significant amount of data has been inserted, updated or deleted. The definition of 'significant' is not immediately obvious. I don't think this is entirely true. On tables that have large numbers of inserts, but no updates or deletes, you do not need to run vacuum. It might be helpful to run analyze on these tables if your inserting enough data to change the statistical relationships, but vacuum itself is not needed. Most tables will *not* be updated frequently in most databases; such tables can be vacuumed irregularly, or vacuumed when the more frequently updated tables are vacuumed. In our specific case we have one table that has a few rows ( 1000), but it is updated as many as 3 times per second. In this case, we chose a 5 minute interval, which results in at worst 1000 'dead' rows in the table as a result of the updates. Since it was such a small table, we saw no reason to vacuum every minute, or even constantly. I have some similar tables in my system, with between 250 and 3500 rows. These tables turn over at least every 15 minutes, so I have decided on a 10 minute vacuum interval. As with Phillip's, since they are small tables, more frequent vacuuming seemed excessive. For larger or more complex tables, the output of VACUUM ANALYZE must be used. snip again, great work Philip. Robert Treat ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html
Re: [HACKERS] DB Tuning Notes for comment...
Robert Treat wrote: On Sun, 2002-12-08 at 09:41, Philip Warner wrote: Any comments or suggestions would be welcome. first and foremost, this is really excellent work! We need to look into getting this info into the standard documentation and/or Bruce's tuning guide. Seconded! Tuning == 1. max_fsm_relations First of all, the free space manager is useless at managing free space if it can not map all relations (including system relations and toast relations). The following query should give the correct ballpark: select count(*) from pg_class where not relkind in ('i','v'); It should be noted that if you have multiple databases, you'll need to get the number of relations minus the system tables for each database, then add in the number of system tables. Set max_fsm_relations to a number greater than this. Add extra to deal with any tables you will create etc. It costs 40 bytes per table, so be generous - if it is set too low, you will get bizarre space usage. 2. VACUUM Frequency --- Ideally VACUUM should run constantly; a future version will support something like it. But for now, vacuum should be run when a significant amount of data has been inserted, updated or deleted. The definition of 'significant' is not immediately obvious. I don't think this is entirely true. On tables that have large numbers of inserts, but no updates or deletes, you do not need to run vacuum. It might be helpful to run analyze on these tables if your inserting enough data to change the statistical relationships, but vacuum itself is not needed. In my experience I've seen tables with numerous indexes continue to benefit greatly from vacuum/vacuum full operations when large volumes of inserts are performed. This is true even when the update/delete activity on the base table itself is manageable. While dropping and recreating the index after loading is possible in some cases, my general comment is that index maintenance is an issue you should keep in mind when designing your vacuum strategy. Most tables will *not* be updated frequently in most databases; such tables can be vacuumed irregularly, or vacuumed when the more frequently updated tables are vacuumed. In our specific case we have one table that has a few rows ( 1000), but it is updated as many as 3 times per second. In this case, we chose a 5 minute interval, which results in at worst 1000 'dead' rows in the table as a result of the updates. Since it was such a small table, we saw no reason to vacuum every minute, or even constantly. I have some similar tables in my system, with between 250 and 3500 rows. These tables turn over at least every 15 minutes, so I have decided on a 10 minute vacuum interval. As with Phillip's, since they are small tables, more frequent vacuuming seemed excessive. For larger or more complex tables, the output of VACUUM ANALYZE must be used. snip again, great work Philip. Robert Treat ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html ss Scott Shattuck Technical Pursuit Inc. ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html
Re: [HACKERS] DB Tuning Notes for comment...
Robert Treat [EMAIL PROTECTED] writes: On Sun, 2002-12-08 at 09:41, Philip Warner wrote: First of all, the free space manager is useless at managing free space if it can not map all relations (including system relations and toast relations). The following query should give the correct ballpark: select count(*) from pg_class where not relkind in ('i','v'); FSM entries aren't needed for sequences either, so more correct is select count(*) from pg_class where relkind in ('r', 't'); It should be noted that if you have multiple databases, you'll need to get the number of relations minus the system tables for each database, then add in the number of system tables. You're assuming that system tables are shared, which they mostly aren't. Summing the pg_class count over all databases (or all that get vacuumed, anyway; you can exclude template0) will be close enough. BTW, this neglects what seems possibly an important factor: you don't need FSM entries for tables that are effectively read-only or insert-only (no deletes or updates). At least in some database designs, that's a significant number of tables. However, I suspect that the present FSM code is not very effective at deciding *which* tables to track if it has too few slots, so Philip's advice of make sure there's one for every table may be the best in the near term. But we need to work at improving that logic. I have some uncommitted patches concerning the FSM management heuristics from Stephen Marshall, which I deemed too late/risky for 7.3, but we should get something done for 7.4. Anyone interested in playing around in this area? regards, tom lane ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] DB Tuning Notes for comment...
Scott Shattuck [EMAIL PROTECTED] writes: Robert Treat wrote: I don't think this is entirely true. On tables that have large numbers of inserts, but no updates or deletes, you do not need to run vacuum. In my experience I've seen tables with numerous indexes continue to benefit greatly from vacuum/vacuum full operations when large volumes of inserts are performed. This is true even when the update/delete activity on the base table itself is manageable. This is hard to believe, as VACUUM does not even touch the indexes unless it has found deletable tuples --- and I am quite certain that btree indexes, at least, do not do any VACUUM-time reorganization beyond deleting deletable entries. (I wouldn't swear to it one way or the other for GiST though.) Robert's opinion coincides with what I know of the code. regards, tom lane ---(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] DB Tuning Notes for comment...
Tom Lane wrote: Scott Shattuck [EMAIL PROTECTED] writes: Robert Treat wrote: I don't think this is entirely true. On tables that have large numbers of inserts, but no updates or deletes, you do not need to run vacuum. In my experience I've seen tables with numerous indexes continue to benefit greatly from vacuum/vacuum full operations when large volumes of inserts are performed. This is true even when the update/delete activity on the base table itself is manageable. This is hard to believe, as VACUUM does not even touch the indexes unless it has found deletable tuples --- and I am quite certain that btree indexes, at least, do not do any VACUUM-time reorganization beyond deleting deletable entries. (I wouldn't swear to it one way or the other for GiST though.) Robert's opinion coincides with what I know of the code. Willing to learn here but skipping a vacuum full has caused some issues for us. Here's some data from a recent 3 day test run that was done with regular vacuums but not vacuum fulls. When running with vacuum full the indexes remain in line: nsuite-10=# select relname, relpages, reltuples from pg_class where relname not like 'pg_%' order by reltuples desc; -[ RECORD 1 ]-- relname | directory_fullpath_ix relpages | 96012 reltuples | 1.38114e+06 -[ RECORD 2 ]-- relname | directory_pkey relpages | 16618 reltuples | 1.38114e+06 -[ RECORD 3 ]-- relname | directory relpages | 23924 reltuples | 59578 snip Needless to say, the system performance was pathetic but the test did serve to highlight this index issue. Anyone want to give a quick summary of index maintenance or give me a pointer into the codebase where someone who's not a C expert might still get a sense of what's being done? I'd really like to understand how an index can get so completely out of whack after a weekend of testing. It seems you're telling me that the data here proves there's an update or delete going on somewhere in the system, even though this test is of a database initialization driven by a stored procedure with no update or delete operations targeting the directory table. There may be some operations being done external to that process that I've not been made aware of but I'm still curious to learn more about indexing behavior so I know why something like this happens in the first place. ss ---(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] DB Tuning Notes for comment...
Scott Shattuck [EMAIL PROTECTED] writes: Willing to learn here but skipping a vacuum full has caused some issues for us. Here's some data from a recent 3 day test run that was done with regular vacuums but not vacuum fulls. When running with vacuum full the indexes remain in line: nsuite-10=# select relname, relpages, reltuples from pg_class where relname not like 'pg_%' order by reltuples desc; -[ RECORD 1 ]-- relname | directory_fullpath_ix relpages | 96012 reltuples | 1.38114e+06 -[ RECORD 2 ]-- relname | directory_pkey relpages | 16618 reltuples | 1.38114e+06 -[ RECORD 3 ]-- relname | directory relpages | 23924 reltuples | 59578 snip blink There's no way that the index and table tuple counts should get that far out of line; in the absence of any concurrent updates, they should be *equal* (or index table, if you have a partial index, which I assume these are not). I would credit the recorded index count exceeding the recorded table count by the number of tuples inserted/ updated while a (plain) VACUUM is in process on that table --- but this doesn't look like it meets that situation. There was a bug a long time ago wherein vacuum would forget to update pg_class.reltuples for indexes in some cases, but according to the CVS logs that was fixed before 7.2 release. What version are you running exactly? In any case, you seem to be dealing with some kind of bug here. It might be helpful to look at the output of vacuum verbose directory if you still have it available. regards, tom lane ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] DB Tuning Notes for comment...
At 03:54 PM 9/12/2002 -0500, Tom Lane wrote: However, I suspect that the present FSM code is not very effective at deciding *which* tables to track if it has too few slots, You are definitely right there. I think it would be worth looking at removing max_fsm_tables as a tuning option, and adding a 'relhasfsm' flag to pg_class for those tables that should not be mapped. Default to 't'. Then, make the table grow dynamically as tables are added, or when a VACUUM occurs... AFAICT, the only justification for a smaller list of relations is for those that are *almost never* subject to deletes or updates. They are certainly common in DB design, but I'd let the DBA designate them. Does this sound reasonable? Philip Warner| __---_ Albatross Consulting Pty. Ltd. |/ - \ (A.B.N. 75 008 659 498) | /(@) __---_ Tel: (+61) 0500 83 82 81 | _ \ Fax: (+61) 03 5330 3172 | ___ | Http://www.rhyme.com.au |/ \| |---- PGP key available upon request, | / and from pgp5.ai.mit.edu:11371 |/ ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] DB Tuning Notes for comment...
At 02:46 PM 9/12/2002 -0500, Robert Treat wrote: getting this info into the standard documentation and/or Bruce's tuning guide. I'd vote for the standard docs since it is sufficiently basic as to be needed by most users. We either need a tuning chapter or a new section in runtime configuration. Philip Warner| __---_ Albatross Consulting Pty. Ltd. |/ - \ (A.B.N. 75 008 659 498) | /(@) __---_ Tel: (+61) 0500 83 82 81 | _ \ Fax: (+61) 03 5330 3172 | ___ | Http://www.rhyme.com.au |/ \| |---- PGP key available upon request, | / and from pgp5.ai.mit.edu:11371 |/ ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html
Re: [HACKERS] DB Tuning Notes for comment...
Philip Warner [EMAIL PROTECTED] writes: I think it would be worth looking at removing max_fsm_tables as a tuning option, and adding a 'relhasfsm' flag to pg_class for those tables that should not be mapped. Default to 't'. Then, make the table grow dynamically as tables are added, or when a VACUUM occurs... If we could make the table grow dynamically then there'd not be much need for the config parameters at all. The real problem is to fit into a shmem segment whose size has to be frozen at postmaster start (which, not incidentally, is before we've ever looked at the database...). We could make the constraint be on total space for relation entries + page entries rather than either individually, but I think that'd mostly make it harder to interpret the config setting rather than offer any real ease of administration. AFAICT, the only justification for a smaller list of relations is for those that are *almost never* subject to deletes or updates. They are certainly common in DB design, but I'd let the DBA designate them. It doesn't seem to me to be that hard for the system to recognize them automatically. Basically, if there are no holes of useful size in the table, there's no need to create an FSM entry for it. The trick is useful size here --- but VACUUM already does the work needed to estimate an average tuple size, so I'd think it could do a reasonably good job of realizing that all the available holes are just leftover space. (The relation's very last page is also a special case that's likely not special-cased correctly at the moment: perhaps it should never be entered in FSM at all, certainly not if it's the only page that would be entered.) regards, tom lane ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [HACKERS] DB Tuning Notes for comment...
At 03:54 PM 9/12/2002 -0500, Tom Lane wrote: FSM entries aren't needed for sequences either, so more correct is select count(*) from pg_class where relkind in ('r', 't'); presumably: select count(*) from pg_class where relkind in ('r', 't', 'i'); Philip Warner| __---_ Albatross Consulting Pty. Ltd. |/ - \ (A.B.N. 75 008 659 498) | /(@) __---_ Tel: (+61) 0500 83 82 81 | _ \ Fax: (+61) 03 5330 3172 | ___ | Http://www.rhyme.com.au |/ \| |---- PGP key available upon request, | / and from pgp5.ai.mit.edu:11371 |/ ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])
Re: [HACKERS] DB Tuning Notes for comment...
Philip Warner [EMAIL PROTECTED] writes: At 03:54 PM 9/12/2002 -0500, Tom Lane wrote: FSM entries aren't needed for sequences either, so more correct is select count(*) from pg_class where relkind in ('r', 't'); presumably: select count(*) from pg_class where relkind in ('r', 't', 'i'); No, I meant what I said. Indexes don't use the FSM. (The premise of the FSM is that one bit of free space in a table is as good as any other bit; a premise quite incorrect for indexes.) regards, tom lane ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] DB Tuning Notes for comment...
At 07:01 PM 9/12/2002 -0500, Tom Lane wrote: We could make the constraint be on total space for relation entries + page entries rather than either individually, but I think that'd mostly make it harder to interpret the config setting rather than offer any real ease of administration. Perhaps doing both? And issue a warning to the logs when max_fsm_relations is borrowing from max_fsm_pages. It might be that the outstanding patches address the problem, but at the moment the choice of which relations to include is not well made when max_fsm_relations of much too small. We should at least issue a warning; but allowing max_fsm_relations to borrow from max_fsm_pages seems like a good idea, since having the number too low (with 161 relations setting it to the default of 100) is useless. Secondly, an empty database contains 98 tables, so the default setting of max_fsm_pages to 100 is way too low. The tradeoff of losing 7 pages from the map to include another relation is worth it, especially if the logs contain a warning. But perhaps the test itself is flawed and there is another problem resulting in this behaviour (doing vacuums twice in a row seems to make it use the free space, but I'd guess this is just edge behaviour of the FSM heuristics): Create Table t(i serial, t text); insert into t(t) 47K of UUEncoded jpeg file - ~47K of toast. insert into t(t) select t from t; ...repeat 9 times... create table t1 as select * from t limit 1; ... create table t19 as select * from t limit 1; create table t20(i serial, t text); insert into t20(t) select t from t; ie. build a lot of tables, with two big ones separated by OID (not sure if the last part is relevant). select count(*) from pg_class where relkind in ('t','r'); in my case this resulted in 161, so I set max_fsm_relations to 100 (ie. not a borderline case, but the default setting). I also left max_fsm_pages at 1 so that we should have space for several thousand rows. Stop start postmaster, then vacuum full to be comfortable no other problems occur, an look at file sizes of relation file and toast file. Now: delete from t where i = 128; delete from t20 where i = 128; vacuum; check file sizes - no surprises, they should be unchanged. Tue Dec 10 12:03:53 EST 2002 -rw---1 pjw users 65536 2002-12-10 12:03 16979 -rw---1 pjw users 65536 2002-12-10 12:03 33432 -rw---1 pjw users67108864 2002-12-10 12:03 16982 -rw---1 pjw users67108864 2002-12-10 12:03 33435 then do: insert into t(t) select t from t20 limit 10; insert into t20(t) select t from t limit 10; and both files have grown: Tue Dec 10 12:08:20 EST 2002 -rw---1 pjw users 65536 2002-12-10 12:08 33432 -rw---1 pjw users67764224 2002-12-10 12:08 33435 -rw---1 pjw users67764224 2002-12-10 12:08 16982 -rw---1 pjw users 65536 2002-12-10 12:08 16979 oddly (bug? edge behaviour?) doing two vacuums in a row results in the free space being used. Philip Warner| __---_ Albatross Consulting Pty. Ltd. |/ - \ (A.B.N. 75 008 659 498) | /(@) __---_ Tel: (+61) 0500 83 82 81 | _ \ Fax: (+61) 03 5330 3172 | ___ | Http://www.rhyme.com.au |/ \| |---- PGP key available upon request, | / and from pgp5.ai.mit.edu:11371 |/ ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] DB Tuning Notes for comment...
At 12:17 PM 10/12/2002 +1100, Philip Warner wrote: Secondly, an empty database contains 98 tables, Corrected based on Tom's later mail; from the FSM PoV, it contains 37 (indices don't count). So it is exhausted when more than two DBs are created. Philip Warner| __---_ Albatross Consulting Pty. Ltd. |/ - \ (A.B.N. 75 008 659 498) | /(@) __---_ Tel: (+61) 0500 83 82 81 | _ \ Fax: (+61) 03 5330 3172 | ___ | Http://www.rhyme.com.au |/ \| |---- PGP key available upon request, | / and from pgp5.ai.mit.edu:11371 |/ ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] DB Tuning Notes for comment...
Philip Warner [EMAIL PROTECTED] writes: Secondly, an empty database contains 98 tables, so the default setting of max_fsm_pages to 100 is way too low. Only 37 of them need FSM entries, but still a good point; we should probably bump it up to 1000 to be more realistic. oddly (bug? edge behaviour?) doing two vacuums in a row results in the free space being used. I'm on my way out the door, so no time to think about what's actually happening in the current code, but ideally I would think that when the FSM doesn't have enough space, it should prefer to remember info about rels with heavy update activity (which might be approximated by rels with lots of free space, but isn't really the same thing). A VACUUM done just after startup does not have any historical info to base this decision on. So it's not unreasonable for the system to make better choices after it's been running awhile than when it's freshly booted. I'm not sure that this is actually what's happening today, just pointing out that I don't consider it a bug per se if the code behaves that way. (The existing code does have some LRU effects, IIRC, but not sure if they account for what you see.) regards, tom lane ---(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] DB Tuning Notes for comment...
Tom Lane wrote: Scott Shattuck [EMAIL PROTECTED] writes: Willing to learn here but skipping a vacuum full has caused some issues for us. Here's some data from a recent 3 day test run that was done with regular vacuums but not vacuum fulls. When running with vacuum full the indexes remain in line: nsuite-10=# select relname, relpages, reltuples from pg_class where relname not like 'pg_%' order by reltuples desc; -[ RECORD 1 ]-- relname | directory_fullpath_ix relpages | 96012 reltuples | 1.38114e+06 -[ RECORD 2 ]-- relname | directory_pkey relpages | 16618 reltuples | 1.38114e+06 -[ RECORD 3 ]-- relname | directory relpages | 23924 reltuples | 59578 snip blink There's no way that the index and table tuple counts should get that far out of line; in the absence of any concurrent updates, they should be *equal* (or index table, if you have a partial index, which I assume these are not). I would credit the recorded index count exceeding the recorded table count by the number of tuples inserted/ updated while a (plain) VACUUM is in process on that table --- but this doesn't look like it meets that situation. There was a bug a long time ago wherein vacuum would forget to update pg_class.reltuples for indexes in some cases, but according to the CVS logs that was fixed before 7.2 release. What version are you running exactly? test=# select version(); version - PostgreSQL 7.2.2 on i686-pc-linux-gnu, compiled by GCC 2.96 (1 row) test=# In any case, you seem to be dealing with some kind of bug here. It might be helpful to look at the output of vacuum verbose directory if you still have it available. NOTICE: --Relation directory-- NOTICE: Index directory_pkey: Pages 15628; Tuples 4988848: Deleted 35407. CPU 0.73s/3.00u sec elapsed 40.53 sec. NOTICE: Index directory_fullpath_ix: Pages 80808; Tuples 4989317: Deleted 35407. CPU 4.84s/3.91u sec elapsed 275.66 sec. NOTICE: Removed 35407 tuples in 786 pages. CPU 0.13s/0.11u sec elapsed 1.80 sec. NOTICE: Pages 80156: Changed 18, Empty 0; Tup 4988787: Vac 35407, Keep 4977704, UnUsed 348422. Total CPU 7.85s/7.58u sec elapsed 343.84 sec. regards, tom lane Thanks for any insight you can offer here. ss ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [HACKERS] DB Tuning Notes for comment...
At 08:39 PM 9/12/2002 -0500, Tom Lane wrote: A VACUUM done just after startup does not have any historical info to base this decision on. The actual order is: start delete vacuum; insert - does not use free space vacuum; insert - does not use free space vacuum; vacuum; insert - uses free space my guess is the fact that the second vacuum has no useful statistics means that (somehow) it is choosing the tables with free space -- perhaps because they are the largest? Philip Warner| __---_ Albatross Consulting Pty. Ltd. |/ - \ (A.B.N. 75 008 659 498) | /(@) __---_ Tel: (+61) 0500 83 82 81 | _ \ Fax: (+61) 03 5330 3172 | ___ | Http://www.rhyme.com.au |/ \| |---- PGP key available upon request, | / and from pgp5.ai.mit.edu:11371 |/ ---(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] DB Tuning Notes for comment...
On Mon, 09 Dec 2002 19:10:23 -0500, Tom Lane wrote: Philip Warner [EMAIL PROTECTED] writes: I think it would be worth looking at removing max_fsm_tables as a tuning option, and adding a 'relhasfsm' flag to pg_class for those tables that should not be mapped. Default to 't'. Then, make the table grow dynamically as tables are added, or when a VACUUM occurs... If we could make the table grow dynamically then there'd not be much need for the config parameters at all. The real problem is to fit into a shmem segment whose size has to be frozen at postmaster start (which, not incidentally, is before we've ever looked at the database...). We could make the constraint be on total space for relation entries + page entries rather than either individually, but I think that'd mostly make it harder to interpret the config setting rather than offer any real ease of administration. Can we not just have vacuum of a database return a total # of pages modified and relations modified, and then report suggested free space map settings? Even this little bit would be a step in the right direction. Robert Treat ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] DB Tuning Notes for comment...
At 09:10 PM 9/12/2002 -0500, Robert Treat wrote: Even this little bit would be a step in the right direction. What I would find really useful is a 'VACUUM...WITH HISORY' which wrote the underlying details of VACUUM VERBOSE to a 'pg_vacuum_history' table. Philip Warner| __---_ Albatross Consulting Pty. Ltd. |/ - \ (A.B.N. 75 008 659 498) | /(@) __---_ Tel: (+61) 0500 83 82 81 | _ \ Fax: (+61) 03 5330 3172 | ___ | Http://www.rhyme.com.au |/ \| |---- PGP key available upon request, | / and from pgp5.ai.mit.edu:11371 |/ ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send unregister YourEmailAddressHere to [EMAIL PROTECTED])