Hi, Note that I've added a few questions to individuals involved with specific points. If you're in the To: list, please search for your name.
On 2019-05-11 16:33:24 -0400, Bruce Momjian wrote: > I have posted a draft copy of the PG 12 release notes here: > > http://momjian.us/pgsql_docs/release-12.html > They are committed to git. Thanks! <title>Migration to Version 12</title> There's a number of features in the compat section that are more general improvements with a side of incompatibility. Won't it be confusing to e.g. have have the ryu floating point conversion speedups in the compat section, but not in the "General Performance" section? <para> Remove the special behavior of <link linkend="datatype-oid">OID</link> columns (Andres Freund, John Naylor) </para> Should we mention that tables with OIDs have to have their oids removed before they can be upgraded? <para> Refactor <link linkend="functions-geometry">geometric functions</link> and operators (Emre Hasegeli) </para> <para> This could lead to more accurate, but slightly different, results from previous releases. </para> </listitem> <listitem> <!-- Author: Tomas Vondra <tomas.von...@postgresql.org> 2018-08-16 [c4c340088] Use the built-in float datatypes to implement geometric --> <para> Restructure <link linkend="datatype-geometric">geometric types</link> to handle NaN, underflow, overflow and division by zero more consistently (Emre Hasegeli) </para> </listitem> <listitem> <!-- Author: Tomas Vondra <tomas.von...@postgresql.org> 2018-09-26 [2e2a392de] Fix problems in handling the line data type --> <para> Improve behavior and error reporting for the <link linkend="datatype-geometric">line data type</link> (Emre Hasegeli) </para> </listitem> Is that sufficient explanation? Feels like we need to expand a bit more. In particular, is it possible that a subset of the changes here require reindexing? Also, aren't three different entries a bit too much? <para> Avoid performing unnecessary rounding of <link linkend="datatype-float"><type>REAL</type></link> and <type>DOUBLE PRECISION</type> values (Andrew Gierth) </para> <para> This dramatically speeds up processing of floating-point values but causes additional trailing digits to potentially be displayed. Users wishing to have output that is rounded to match the previous behavior can set <link linkend="guc-extra-float-digits"><literal>extra_float_digits=0</literal></link>, which is no longer the default. </para> </listitem> Isn't it exactly the *other* way round? *Previously* we'd output additional trailing digits. The new algorithm instead will instead have *exactly* the required number of digits? <listitem> <!-- Author: Tom Lane <t...@sss.pgh.pa.us> 2019-02-11 [1d92a0c9f] Redesign the partition dependency mechanism. --> <para> Improve handling of partition dependency (Tom Lane) </para> <para> This prevents the creation of inconsistent partition hierarchies in rare cases. </para> </listitem> That seems not very informative for users? <listitem> <!-- Author: Alexander Korotkov <akorot...@postgresql.org> 2018-07-28 [d2086b08b] Reduce path length for locking leaf B-tree pages during Author: Peter Geoghegan <p...@bowt.ie> 2019-03-25 [f21668f32] Add "split after new tuple" nbtree optimization. --> <para> Improve speed of btree index insertions (Peter Geoghegan, Alexander Korotkov) </para> <para> The new code improves the space-efficiency of page splits, reduces locking overhead, and gives better performance for <command>UPDATE</command>s and <command>DELETE</command>s on indexes with many duplicates. </para> </listitem> <listitem> <!-- Author: Peter Geoghegan <p...@bowt.ie> 2019-03-20 [dd299df81] Make heap TID a tiebreaker nbtree index column. Author: Peter Geoghegan <p...@bowt.ie> 2019-03-20 [fab250243] Consider secondary factors during nbtree splits. --> <para> Have new btree indexes sort duplicate index entries in heap-storage order (Peter Geoghegan, Heikki Linnakangas) </para> <para> Indexes <application>pg_upgraded</application> from previous releases will not have this ordering. </para> </listitem> I'm not sure that the grouping here is quite right. And the second entry probably should have some explanation about the benefits? <listitem> <!-- Author: Peter Eisentraut <pete...@gmx.net> 2018-11-14 [1b5d797cd] Lower lock level for renaming indexes --> <para> Reduce locking requirements for index renaming (Peter Eisentraut) </para> </listitem> Should we specify the newly required lock level? Because it's quire relevant for users what exactly they're now able to do concurrently in operation? <para> Allow <link linkend="queries-with">common table expressions</link> (<acronym>CTE</acronym>) to be inlined in later parts of the query (Andreas Karlsson, Andrew Gierth, David Fetter, Tom Lane) </para> <para> Specifically, <acronym>CTE</acronym>s are inlined if they are not recursive and are referenced only once later in the query. Inlining can be prevented by specifying <literal>MATERIALIZED</literal>, and forced by specifying <literal>NOT MATERIALIZED</literal>. Previously, <acronym>CTE</acronym>s were never inlined and were always evaluated before the rest of the query. </para> Hm. Is it actually correct to say that "were always evaluated before the rest of the query."? My understanding is that that's not actually how they behaved. Materialization for CTE scans was on-demand (i.e. when needed by a CTE scan), and even for DML CTEs we'd only force the underlying query to completion at the end of the query? <listitem> <!-- Author: Tom Lane <t...@sss.pgh.pa.us> 2019-02-09 [1fb57af92] Create the infrastructure for planner support functions. --> <para> Add support for <link linkend="sql-createfunction">function selectivity</link> (Tom Lane) </para> </listitem> Hm, that message doesn't seem like an accurate description of that commit (if anything it's a391ff3c?). Given that it all requires C hackery, perhaps we ought to move it to the source code section? And isn't the most important part of this set of changes commit 74dfe58a5927b22c744b29534e67bfdd203ac028 Author: Tom Lane <t...@sss.pgh.pa.us> Date: 2019-02-11 21:26:08 -0500 Allow extensions to generate lossy index conditions. <listitem> <!-- Author: Tomas Vondra <tomas.von...@postgresql.org> 2019-01-29 [36a1281f8] Separate per-batch and per-tuple memory contexts in COPY Author: Heikki Linnakangas <heikki.linnakan...@iki.fi> 2019-01-25 [9556aa01c] Use single-byte Boyer-Moore-Horspool search even with mu Author: Andres Freund <and...@anarazel.de> 2019-01-26 [a9c35cf85] Change function call information to be variable length. --> <para> Greatly reduce memory consumption of <xref linkend="sql-copy"/> and function calls (Andres Freund, Tomas Vondra, Tom Lane) </para> </listitem> Grouping these three changes together makes no sense to me. I think the first commit just ought not to be mentioned separately, it's just a fix for a memory leak in 31f3817402, essentially a 12 only bugfix? The second commit is about position() etc, which seems not to match that description either? The third is probably more appropriate to be in the source code section. While it does speed up function calls a bit (in particular plpgsql which is very function call heavy), it also is a breaking change for some external code? Not sure why Tom is listed with this entry? <listitem> <!-- Author: Heikki Linnakangas <heikki.linnakan...@iki.fi> 2019-01-25 [9556aa01c] Use single-byte Boyer-Moore-Horspool search even with mu --> <para> Improve search performance for multi-byte characters (Heikki Linnakangas) </para> </listitem> That's the second reference to the commit. I suspect this is much better separate, so I'd just remove it from above. <listitem> <!-- Author: Stephen Frost <sfr...@snowman.net> 2019-04-02 [4d0e994ee] Add support for partial TOAST decompression --> <para> Allow <link linkend="storage-toast"><literal>TOAST</literal></link> values to be minimally decompressed (Paul Ramsey) </para> I'd s/minimal/partial/ - I don't think the code guarantees anything about it being minimal? And "minimally decompressed" also is somewhat confusing, because it sounds like it's about the compression quality rather than only decompressing part of the data. <listitem> <!-- Author: Michael Paquier <mich...@paquier.xyz> 2018-08-10 [f841ceb26] Improve TRUNCATE by avoiding early lock queue --> <para> Prevent <xref linkend="sql-truncate"/> from requesting a lock on tables for which it lacks permission (Michaël Paquier) </para> <para> This prevents unauthorized locking delays. </para> </listitem> <listitem> <!-- Author: Michael Paquier <mich...@paquier.xyz> 2018-08-27 [a556549d7] Improve VACUUM and ANALYZE by avoiding early lock queue --> <para> Prevent <command>VACUUM</command> and <command>ANALYZE</command> from requesting a lock on tables for which it lacks permission (Michaël Paquier) </para> <para> This prevents unauthorized locking delays. </para> </listitem> I don't think this should be in the <title><acronym>Authentication</acronym></title> section. Also perhaps, s/it/the user/, or "the caller"? <listitem> <!-- Author: Tom Lane <t...@sss.pgh.pa.us> 2019-03-10 [cbccac371] Reduce the default value of autovacuum_vacuum_cost_delay --> <para> Reduce the default value of <xref linkend="guc-autovacuum-vacuum-cost-delay"/> to 2ms (Tom Lane) </para> </listitem> I think this needs to explain that this can increase autovacuum's IO throughput considerably. <listitem> <!-- Author: Tom Lane <t...@sss.pgh.pa.us> 2019-03-10 [caf626b2c] Convert [autovacuum_]vacuum_cost_delay into floating-poi --> <para> Allow <xref linkend="guc-vacuum-cost-delay"/> to specify sub-millisecond delays (Tom Lane) </para> <para> Floating-point values can also now be specified. </para> </listitem> And this should be merged with the previous entry? <listitem> <!-- Author: Tom Lane <t...@sss.pgh.pa.us> 2019-03-10 [caf626b2c] Convert [autovacuum_]vacuum_cost_delay into floating-poi --> <para> Allow time-based server variables to use <link linkend="config-setting">micro-seconds</link> (us) (Tom Lane) </para> </listitem> <listitem> <!-- Author: Tom Lane <t...@sss.pgh.pa.us> 2019-03-11 [1a83a80a2] Allow fractional input values for integer GUCs, and impr --> <para> Allow fractional input for integer server variables (Tom Lane) </para> <para> For example, <command>SET work_mem = '30.1GB'</command>. </para> </listitem> <listitem> <!-- Author: Tom Lane <t...@sss.pgh.pa.us> 2019-03-10 [caf626b2c] Convert [autovacuum_]vacuum_cost_delay into floating-poi --> <para> Allow units to be specified for floating-point server variables (Tom Lane) </para> </listitem> Can't we combine these? Seems excessively detailed in comparison to the rest of the entries. <listitem> <!-- Author: Peter Eisentraut <pe...@eisentraut.org> 2019-01-11 [ff8530605] Add value 'current' for recovery_target_timeline --> <para> Add an explicit value of <literal>current</literal> for <xref linkend="guc-recovery-target-time"/> (Peter Eisentraut) </para> </listitem> Seems like this should be combined with the earlier "Cause recovery to advance to the latest timeline by default" entry. <listitem> <!-- Author: Peter Eisentraut <pe...@eisentraut.org> 2019-03-30 [fc22b6623] Generated columns --> <para> Add support for <link linkend="sql-createtable">generated columns</link> (Peter Eisentraut) </para> <para> Rather than storing a value only at row creation time, generated columns are also modified during updates, and can reference other table columns. </para> </listitem> I find this description confusing. How about cribbing from the commit? Roughly like This allows creating columns that are computed from expressions, including references to other columns in the same table, rather than having to be specified by the inserter/updater. Think we also ought to mention that this is only stored generated columns, given that the SQL feature also includes virtual columns? <listitem> <!-- Author: Fujii Masao <fu...@postgresql.org> 2019-04-08 [119dcfad9] Add vacuum_truncate reloption. Author: Fujii Masao <fu...@postgresql.org> 2019-05-08 [b84dbc8eb] Add TRUNCATE parameter to VACUUM. --> <para> Add <xref linkend="sql-vacuum"/> and <command>CREATE TABLE</command> options to prevent <command>VACUUM</command> from truncating trailing empty pages (Tsunakawa Takayuki) </para> <para> The options are <varname>vacuum_truncate</varname> and <varname>toast.vacuum_truncate</varname>. This reduces vacuum locking requirements. </para> </listitem> Maybe add something like: "This can be helpful to avoid query cancellations on standby that are not avoided by hot_standby_feedback."? <listitem> <!-- Author: Robert Haas <rh...@postgresql.org> 2019-04-04 [a96c41fee] Allow VACUUM to be run with index cleanup disabled. --> <para> Allow vacuum to avoid index cleanup with the <literal>INDEX_CLEANUP</literal> option (Masahiko Sawada) </para> </listitem> I think we ought to expand a bit more on why one would do that, including perhaps some caveat? <listitem> <!-- Author: Peter Eisentraut <pe...@eisentraut.org> 2019-03-19 [590a87025] Ignore attempts to add TOAST table to shared or catalog --> <para> Allow modifications of system tables using <xref linkend="sql-altertable"/> (Peter Eisentraut) </para> <para> This allows modifications of <literal>reloptions</literal> and autovacuum settings. </para> </listitem> I think the first paragraph is a bit dangerous. This does *not* generally allow modifications of system tables using ALTER TABLE. <listitem> <!-- Author: Tom Lane <t...@sss.pgh.pa.us> 2019-01-30 [5f5c01459] Allow RECORD and RECORD[] to be specified in function co --> <para> Allow <type>RECORD</type> and <type>RECORD[]</type> to be specified as a function <link linkend="sql-createfunction">return-value record</link> (Elvis Pranskevichus) </para> <para> DETAIL? </para> </listitem> This description doesn't sound accurate to me. Tom? <listitem> <!-- Author: Tom Lane <t...@sss.pgh.pa.us> 2018-09-25 [5b7e03670] Avoid unnecessary precision loss for pgbench's - -rate ta --> <para> Compute behavior based on pgbench's <option>--rate</option> value more precisely (Tom Lane) </para> </listitem> "Computing behavior" sounds a bit odd. Maybe "Improve precision of pgbench's <option>--rate</option>" option? <listitem> <!-- Author: Thomas Munro <tmu...@postgresql.org> 2018-07-13 [387a5cfb9] Add pg_dump - -on-conflict-do-nothing option. --> <para> Allow restoration of an <command>INSERT</command>-statement dump to skip rows which would cause conflicts (Surafel Temesgen) </para> <para> The <application>pg_dump</application> option is <option>--on-conflict-do-nothing</option>. </para> </listitem> Hm, this doesn't seem that clear. It's not really a restoration time option, and it sounds a bit like that in the above. How about instead saying something like: Allow pg_dump to emit INSERT ... ON CONFLICT DO NOTHING (Surafel). <listitem> <!-- Author: Andrew Dunstan <and...@dunslane.net> 2019-02-18 [af25bc03e] Provide an extra-float-digits setting for pg_dump / pg_d --> <para> Allow the number of float digits to be specified for <application>pg_dump</application> and <application>pg_dumpall</application> (Andrew Dunstan) </para> <para> This allows the float digit output to match previous dumps. </para> Hm, feels like that should be combined with the ryu compat entry? <para> Add <xref linkend="sql-create-access-method"/> command to create new table types (Haribabu Kommi, Andres Freund, Álvaro Herrera, Dimitri Dolgov) </para> A few points: 1) Is this really source code, given that CREATE ACCESS METHOD TYPE TABLE is a DDL command, and USING (...) for CREATE TABLE etc is an option to DDL commands? 2) I think the description sounds a bit too much like it's about new forms of tables, rather than their storage. How about something roughly like: Allow different <link linkend="tableam">table access methods</> to be <link linkend="sql-create-access-method>created</> and <link linkend="sql-createtable-method">used</>. This allows to develop and use new ways of storing and accessing table data, optimized for different use-cases, without having to modify PostgreSQL. The existing <literal>heap</literal> access method remains the default. 3) This misses a large set of commits around making tableam possible, in particular the commits around commit 4da597edf1bae0cf0453b5ed6fc4347b6334dfe1 Author: Andres Freund <and...@anarazel.de> Date: 2018-11-16 16:35:11 -0800 Make TupleTableSlots extensible, finish split of existing slot type. Given that those commits entail an API break relevant for extensions, should we have them as a separate "source code" note? 4) I think the attribution isn't quite right. For one, a few names with substantial work are missing (Amit Khandekar, Ashutosh Bapat, Alexander Korotkov), and the order doesn't quite seem right. On the latter part I might be somewhat petty, but I spend *many* months of my life on this. How about: Andres Freund, Haribabu Kommi, Alvaro Herrera, Alexander Korotkov, David Rowley, Dimitri Golgov if we keep 3) separate and Andres Freund, Haribabu Kommi, Alvaro Herrera, Ashutosh Bapat, Alexander Korotkov, Amit Khandekar, David Rowley, Dimitri Golgov otherwise? I think it might actually make sense to take David off this list, because his tableam work is essentially part of it's own entry, as <!-- Author: Peter Eisentraut <pete...@gmx.net> 2018-08-01 [0d5f05cde] Allow multi-inserts during COPY into a partitioned table --> <para> Improve speed of <command>COPY</command> into partitioned tables (David Rowley) </para> since his copy.c portions of 86b85044e823a largely are a rewrite of the above commit. <listitem> <!-- Author: Greg Stark <st...@mit.edu> 2018-10-09 [36e9d413a] Add "B" suffix for bytes to docs --> <para> Document that the <literal>B</literal>/bytes units can be specified for <link linkend="config-setting">server variables</link> (Greg Stark) </para> </listitem> Given how large changes we skip over in the release notes, I don't really see a point in including changes like this. Feels like we'd at the very least also have to include larger changes with typo/grammar fixes etc? Greetings, Andres Freund
