On Wed, Nov 25, 2020 at 1:13 PM Fujii Masao <masao.fu...@oss.nttdata.com> wrote:
> > > On 2020/11/24 23:14, Fujii Masao wrote: > > > > > > On 2020/11/19 14:33, torikoshia wrote: > >> On 2020-11-18 11:35, Fujii Masao wrote: > >> > >> Thanks for your comment! > >> > >>> On 2020/11/18 11:04, torikoshia wrote: > >>>> Hi, > >>>> > >>>> AFAIU, when the planner statistics are updated, generic plans are > invalidated and PostgreSQL recreates. However, the manual doesn't seem to > explain it explicitly. > >>>> > >>>> https://www.postgresql.org/docs/devel/sql-prepare.html > >>>> > >>>> I guess this case is included in 'whenever database objects used in > the statement have definitional (DDL) changes undergone', but I feel it's > hard to infer. > >>>> > >>>> Since updates of the statistics can often happen, how about > describing this case explicitly like an attached patch? > >>> > >>> +1 to add that note. > >>> > >>> - statement. Also, if the value of <xref > linkend="guc-search-path"/> changes > >>> + statement. For example, when the planner statistics of the > statement > >>> + are updated, <productname>PostgreSQL</productname> re-analyzes and > >>> + re-plans the statement. > >>> > >>> I don't think "For example," is necessary. > >>> > >>> "planner statistics of the statement" sounds vague? Does the statement > >>> is re-analyzed and re-planned only when the planner statistics of > database > >>> objects used in the statement are updated? If yes, we should describe > >>> that to make the note a bit more explicitly? > >> > >> Yes. As far as I confirmed, updating statistics which are not used in > >> prepared statements doesn't trigger re-analyze and re-plan. > >> > >> Since plan invalidations for DDL changes and statistcal changes are > caused > >> by PlanCacheRelCallback(Oid 'relid'), only the prepared statements using > >> 'relid' relation seem invalidated.> Attached updated patch. > > > > Thanks for confirming that and updating the patch! > > force re-analysis and re-planning of the statement before using it > whenever database objects used in the statement have undergone > definitional (DDL) changes since the previous use of the prepared > - statement. Also, if the value of <xref linkend="guc-search-path"/> > changes > + statement. Similarly, whenever the planner statistics of database > + objects used in the statement have updated, re-analysis and re-planning > + happen. > > "been" should be added between "have" and "updated" in the above "objects > used in the statement have updated"? > > I'm inclined to add "since the previous use of the prepared statement" into > also the second description, to make it clear. But if we do that, it's > better > to merge the above two description into one, as follows? > > whenever database objects used in the statement have undergone > - definitional (DDL) changes since the previous use of the prepared > + definitional (DDL) changes or the planner statistics of them have > + been updated since the previous use of the prepared > statement. Also, if the value of <xref linkend="guc-search-path"/> > changes > > > +1 for documenting this case since I just spent time reading code last week for it. and +1 for the above sentence to describe this case. -- Best Regards Andy Fan
