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pgsql: Improve documentation about MVCC-unsafe utility commands. 7+ messages / 1 participants [nested] [flat]
* pgsql: Improve documentation about MVCC-unsafe utility commands. @ 2015-08-15 17:30 Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 0 replies; 7+ messages in thread From: Tom Lane @ 2015-08-15 17:30 UTC (permalink / raw) To: pgsql-committers Improve documentation about MVCC-unsafe utility commands. The table-rewriting forms of ALTER TABLE are MVCC-unsafe, in much the same way as TRUNCATE, because they replace all rows of the table with newly-made rows with a new xmin. (Ideally, concurrent transactions with old snapshots would continue to see the old table contents, but the data is not there anymore --- and if it were there, it would be inconsistent with the table's updated rowtype, so there would be serious implementation problems to fix.) This was nowhere documented though, and the problem was only documented for TRUNCATE in a note in the TRUNCATE reference page. Create a new "Caveats" section in the MVCC chapter that can be home to this and other limitations on serializable consistency. In passing, fix a mistaken statement that VACUUM and CLUSTER would reclaim space occupied by a dropped column. They don't reconstruct existing tuples so they couldn't do that. Back-patch to all supported branches. Branch ------ master Details ------- http://git.postgresql.org/pg/commitdiff/5869cbfef48fdfa6b8f108c6c395601e8ad27250 Modified Files -------------- doc/src/sgml/mvcc.sgml | 46 ++++++++++++++++++++++++++----------- doc/src/sgml/ref/alter_table.sgml | 21 +++++++++++------ doc/src/sgml/ref/truncate.sgml | 23 +++++-------------- 3 files changed, 52 insertions(+), 38 deletions(-) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers ^ permalink raw reply [nested|flat] 7+ messages in thread
* pgsql: Improve documentation about MVCC-unsafe utility commands. @ 2015-08-15 17:30 Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 0 replies; 7+ messages in thread From: Tom Lane @ 2015-08-15 17:30 UTC (permalink / raw) To: pgsql-committers Improve documentation about MVCC-unsafe utility commands. The table-rewriting forms of ALTER TABLE are MVCC-unsafe, in much the same way as TRUNCATE, because they replace all rows of the table with newly-made rows with a new xmin. (Ideally, concurrent transactions with old snapshots would continue to see the old table contents, but the data is not there anymore --- and if it were there, it would be inconsistent with the table's updated rowtype, so there would be serious implementation problems to fix.) This was nowhere documented though, and the problem was only documented for TRUNCATE in a note in the TRUNCATE reference page. Create a new "Caveats" section in the MVCC chapter that can be home to this and other limitations on serializable consistency. In passing, fix a mistaken statement that VACUUM and CLUSTER would reclaim space occupied by a dropped column. They don't reconstruct existing tuples so they couldn't do that. Back-patch to all supported branches. Branch ------ REL9_5_STABLE Details ------- http://git.postgresql.org/pg/commitdiff/656363d83970195e875c5c2153ef097e112b859f Modified Files -------------- doc/src/sgml/mvcc.sgml | 46 ++++++++++++++++++++++++++----------- doc/src/sgml/ref/alter_table.sgml | 21 +++++++++++------ doc/src/sgml/ref/truncate.sgml | 23 +++++-------------- 3 files changed, 52 insertions(+), 38 deletions(-) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers ^ permalink raw reply [nested|flat] 7+ messages in thread
* pgsql: Improve documentation about MVCC-unsafe utility commands. @ 2015-08-15 17:30 Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 0 replies; 7+ messages in thread From: Tom Lane @ 2015-08-15 17:30 UTC (permalink / raw) To: pgsql-committers Improve documentation about MVCC-unsafe utility commands. The table-rewriting forms of ALTER TABLE are MVCC-unsafe, in much the same way as TRUNCATE, because they replace all rows of the table with newly-made rows with a new xmin. (Ideally, concurrent transactions with old snapshots would continue to see the old table contents, but the data is not there anymore --- and if it were there, it would be inconsistent with the table's updated rowtype, so there would be serious implementation problems to fix.) This was nowhere documented though, and the problem was only documented for TRUNCATE in a note in the TRUNCATE reference page. Create a new "Caveats" section in the MVCC chapter that can be home to this and other limitations on serializable consistency. In passing, fix a mistaken statement that VACUUM and CLUSTER would reclaim space occupied by a dropped column. They don't reconstruct existing tuples so they couldn't do that. Back-patch to all supported branches. Branch ------ REL9_4_STABLE Details ------- http://git.postgresql.org/pg/commitdiff/ff2ee45f2f3d528e1c95828a14ca8cbdfb9778d2 Modified Files -------------- doc/src/sgml/mvcc.sgml | 46 ++++++++++++++++++++++++++----------- doc/src/sgml/ref/alter_table.sgml | 21 +++++++++++------ doc/src/sgml/ref/truncate.sgml | 23 +++++-------------- 3 files changed, 52 insertions(+), 38 deletions(-) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers ^ permalink raw reply [nested|flat] 7+ messages in thread
* pgsql: Improve documentation about MVCC-unsafe utility commands. @ 2015-08-15 17:30 Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 0 replies; 7+ messages in thread From: Tom Lane @ 2015-08-15 17:30 UTC (permalink / raw) To: pgsql-committers Improve documentation about MVCC-unsafe utility commands. The table-rewriting forms of ALTER TABLE are MVCC-unsafe, in much the same way as TRUNCATE, because they replace all rows of the table with newly-made rows with a new xmin. (Ideally, concurrent transactions with old snapshots would continue to see the old table contents, but the data is not there anymore --- and if it were there, it would be inconsistent with the table's updated rowtype, so there would be serious implementation problems to fix.) This was nowhere documented though, and the problem was only documented for TRUNCATE in a note in the TRUNCATE reference page. Create a new "Caveats" section in the MVCC chapter that can be home to this and other limitations on serializable consistency. In passing, fix a mistaken statement that VACUUM and CLUSTER would reclaim space occupied by a dropped column. They don't reconstruct existing tuples so they couldn't do that. Back-patch to all supported branches. Branch ------ REL9_3_STABLE Details ------- http://git.postgresql.org/pg/commitdiff/7e451f7dc241b4947843f84b74298f253c898ed1 Modified Files -------------- doc/src/sgml/mvcc.sgml | 46 ++++++++++++++++++++++++++----------- doc/src/sgml/ref/alter_table.sgml | 19 ++++++++++----- doc/src/sgml/ref/truncate.sgml | 23 +++++-------------- 3 files changed, 51 insertions(+), 37 deletions(-) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers ^ permalink raw reply [nested|flat] 7+ messages in thread
* pgsql: Improve documentation about MVCC-unsafe utility commands. @ 2015-08-15 17:30 Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 0 replies; 7+ messages in thread From: Tom Lane @ 2015-08-15 17:30 UTC (permalink / raw) To: pgsql-committers Improve documentation about MVCC-unsafe utility commands. The table-rewriting forms of ALTER TABLE are MVCC-unsafe, in much the same way as TRUNCATE, because they replace all rows of the table with newly-made rows with a new xmin. (Ideally, concurrent transactions with old snapshots would continue to see the old table contents, but the data is not there anymore --- and if it were there, it would be inconsistent with the table's updated rowtype, so there would be serious implementation problems to fix.) This was nowhere documented though, and the problem was only documented for TRUNCATE in a note in the TRUNCATE reference page. Create a new "Caveats" section in the MVCC chapter that can be home to this and other limitations on serializable consistency. In passing, fix a mistaken statement that VACUUM and CLUSTER would reclaim space occupied by a dropped column. They don't reconstruct existing tuples so they couldn't do that. Back-patch to all supported branches. Branch ------ REL9_2_STABLE Details ------- http://git.postgresql.org/pg/commitdiff/ed51165907e5b413cf221bd82c7f4274bf6ab58f Modified Files -------------- doc/src/sgml/mvcc.sgml | 46 ++++++++++++++++++++++++++----------- doc/src/sgml/ref/alter_table.sgml | 19 ++++++++++----- doc/src/sgml/ref/truncate.sgml | 23 +++++-------------- 3 files changed, 51 insertions(+), 37 deletions(-) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers ^ permalink raw reply [nested|flat] 7+ messages in thread
* pgsql: Improve documentation about MVCC-unsafe utility commands. @ 2015-08-15 17:30 Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 0 replies; 7+ messages in thread From: Tom Lane @ 2015-08-15 17:30 UTC (permalink / raw) To: pgsql-committers Improve documentation about MVCC-unsafe utility commands. The table-rewriting forms of ALTER TABLE are MVCC-unsafe, in much the same way as TRUNCATE, because they replace all rows of the table with newly-made rows with a new xmin. (Ideally, concurrent transactions with old snapshots would continue to see the old table contents, but the data is not there anymore --- and if it were there, it would be inconsistent with the table's updated rowtype, so there would be serious implementation problems to fix.) This was nowhere documented though, and the problem was only documented for TRUNCATE in a note in the TRUNCATE reference page. Create a new "Caveats" section in the MVCC chapter that can be home to this and other limitations on serializable consistency. In passing, fix a mistaken statement that VACUUM and CLUSTER would reclaim space occupied by a dropped column. They don't reconstruct existing tuples so they couldn't do that. Back-patch to all supported branches. Branch ------ REL9_1_STABLE Details ------- http://git.postgresql.org/pg/commitdiff/138f76533cdcbf4b6c61ba9f8d92dd74b332ccba Modified Files -------------- doc/src/sgml/mvcc.sgml | 46 ++++++++++++++++++++++++++----------- doc/src/sgml/ref/alter_table.sgml | 19 ++++++++++----- doc/src/sgml/ref/truncate.sgml | 23 +++++-------------- 3 files changed, 51 insertions(+), 37 deletions(-) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers ^ permalink raw reply [nested|flat] 7+ messages in thread
* pgsql: Improve documentation about MVCC-unsafe utility commands. @ 2015-08-15 17:30 Tom Lane <tgl@sss.pgh.pa.us> 0 siblings, 0 replies; 7+ messages in thread From: Tom Lane @ 2015-08-15 17:30 UTC (permalink / raw) To: pgsql-committers Improve documentation about MVCC-unsafe utility commands. The table-rewriting forms of ALTER TABLE are MVCC-unsafe, in much the same way as TRUNCATE, because they replace all rows of the table with newly-made rows with a new xmin. (Ideally, concurrent transactions with old snapshots would continue to see the old table contents, but the data is not there anymore --- and if it were there, it would be inconsistent with the table's updated rowtype, so there would be serious implementation problems to fix.) This was nowhere documented though, and the problem was only documented for TRUNCATE in a note in the TRUNCATE reference page. Create a new "Caveats" section in the MVCC chapter that can be home to this and other limitations on serializable consistency. In passing, fix a mistaken statement that VACUUM and CLUSTER would reclaim space occupied by a dropped column. They don't reconstruct existing tuples so they couldn't do that. Back-patch to all supported branches. Branch ------ REL9_0_STABLE Details ------- http://git.postgresql.org/pg/commitdiff/ec2bc39e8910d05e27794e5095b7b8daed981406 Modified Files -------------- doc/src/sgml/mvcc.sgml | 20 ++++++++++++++++++++ doc/src/sgml/ref/alter_table.sgml | 10 +++++++++- doc/src/sgml/ref/truncate.sgml | 23 ++++++----------------- 3 files changed, 35 insertions(+), 18 deletions(-) -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers ^ permalink raw reply [nested|flat] 7+ messages in thread
end of thread, other threads:[~2015-08-15 17:30 UTC | newest] Thread overview: 7+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2015-08-15 17:30 pgsql: Improve documentation about MVCC-unsafe utility commands. Tom Lane <tgl@sss.pgh.pa.us> 2015-08-15 17:30 pgsql: Improve documentation about MVCC-unsafe utility commands. Tom Lane <tgl@sss.pgh.pa.us> 2015-08-15 17:30 pgsql: Improve documentation about MVCC-unsafe utility commands. Tom Lane <tgl@sss.pgh.pa.us> 2015-08-15 17:30 pgsql: Improve documentation about MVCC-unsafe utility commands. Tom Lane <tgl@sss.pgh.pa.us> 2015-08-15 17:30 pgsql: Improve documentation about MVCC-unsafe utility commands. Tom Lane <tgl@sss.pgh.pa.us> 2015-08-15 17:30 pgsql: Improve documentation about MVCC-unsafe utility commands. Tom Lane <tgl@sss.pgh.pa.us> 2015-08-15 17:30 pgsql: Improve documentation about MVCC-unsafe utility commands. Tom Lane <tgl@sss.pgh.pa.us>
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