Re: Annotated release notes
От | Bruce Momjian |
---|---|
Тема | Re: Annotated release notes |
Дата | |
Msg-id | 200310311926.h9VJQc723546@candle.pha.pa.us обсуждение исходный текст |
Ответ на | Re: Annotated release notes (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: Annotated release notes
(Tom Lane <tgl@sss.pgh.pa.us>)
|
Список | pgsql-docs |
Tom Lane wrote: > Bruce Momjian <pgman@candle.pha.pa.us> writes: > > OK, I have committed changes to release.sgml so most complex entries > > have a paragraph describing the change. You can see the result at: > > http://candle.pha.pa.us/main/writings/pgsql/sgml/release.html#RELEASE-7-4 > > I need people to check this and help me with the items marked 'bjm'. > > Okay, a few comments ... > > <listitem><para> IN/NOT IN subqueries are now much more efficient</para> > <para> > In previous releases, IN/NOT IN subqueries were joined to the > upper query by sequentially scanning the subquery looking for > a join. The 7.4 code uses the same sophisticated techniques > used by ordinary joins and so is much faster, and is now faster > than EXISTS subqueries. > </para> > </listitem> > > This might be overstatement. How about "... is much faster. An IN > will now usually be as fast as or faster than an equivalent EXISTS > subquery; this reverses the conventional wisdom that applied to previous > Postgres releases." > Done. > <listitem><para> Improved GROUP BY processing by using hash buckets</para> > <para> > In previous releases, GROUP BY totals were accumulated by > sequentially scanning the list of groups looking for a match; > the 7.4 code places GROUP BY values in hash buckets so the > proper match can be found much quicker. This is particularly > significant in speeding up queries that have a large > number of distinct GROUP BY values. > </para> > </listitem> > > This is backwards. I suggest "In previous releases, GROUP BY required > sorting the input data to bring group members together. 7.4 can do it > that way, or can accumulate data into per-group hash buckets in-memory. > The hash technique avoids a sort and so can be much faster, if the > number of distinct GROUP BY values is not too large to fit in memory." Done. > <listitem><para> ANSI joins are now better optimized</para> > <para> > Prior releases evaluated ANSI join syntax only in the order > specified by the query; 7.4 allows full optimization of > queries using ANSI join syntax, meaning the optimizer considers > all possible join orderings and chooses the most efficient. > </para> > </listitem> > > This is correct only for inner joins. Outer joins still follow the > syntax-implied ordering. Not sure what the best rewording is. > > <listitem><para> Full support for IPv6 connections and IPv6 address > data types</para> > <para> > Prior releases allowed only IPv6 connections and IP data types only > supported IPv4 addresses. This release adds full IPv6 support in > both of these areas. > </para> > </listitem> > > Surely "allowed only IPv4 connections". Yep, fixed. > <listitem><para> New protocol improves connection speed/reliability, > and adds error codes, status information, a binary protocol, error > reporting verbosity, and cleaner startup packets.</para> > </listitem> > > I dunno anything about improving connection speed/reliability. How > about "New client-to-server protocol adds error codes, more status > information, better support for binary data transmission, parameter > values separated from SQL commands, prepared statements available at the > protocol level, clean recovery from COPY failures, and cleaner startup > packets. The older protocol is still supported by both servers and > clients." Updated with your text. I thought connections were faster because we passed fewer packets on startup, and I thought you measured a speed improvement in connection startup time. Am I remembering wrong? > > <listitem><para>Align shared buffers on 32-byte boundary for copy speed improvement (Manfred Spraul)</para> > <para> > Certain CPU's perform faster data copies when addresses are 32-bit > aligned. > </para> > </listitem> > > bit -> byte Fixed. > <listitem><para>Fix subquery aggregates of upper query columns to match SQL spec. (Tom)</para> > <para> > bjm > </para> > </listitem> > > Try: > > Fix aggregates in subqueries to match SQL spec > > The SQL spec says that an aggregate function appearing within a nested > subquery belongs to the outer query if its argument contains only > outer-query variables. Prior PG releases did not handle this fine point > correctly. Updated. > <listitem><para>Add option to prevent auto-addition of tables referenced in query (Nigel J. > Andrews) </para> > <para> > By default, tables mentioned in the query are automatically added > to the FROM clause if they are not already there. This option > disabled that behavior. > </para> > </listitem> > > I'd suggest "... not already there. This is compatible with > historical Postgres behavior but is contrary to the SQL spec. > This option allows selecting spec-compatible behavior." Updated. > <listitem><para>Multiple pggla_dump fixes, including tar format and large objects</para></listitem> > > "pggla_dump"? Sure, you know, pggla_dump. :-) Fixed. > <listitem><para>Syntax errors now reported as 'syntax error' rather than 'parse error' (Tom)</para></listitem> > > Is it worth giving this its own bullet point? It's far down in the > noise compared to all the other message rewordings. I added it to the compatbility section at the top. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073
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