Thank you both! I think Laurenz’s changes make perfect sense! Sent from my iPhone
> On May 19, 2022, at 8:37 AM, Laurenz Albe <laurenz.a...@cybertec.at> wrote: > > On Thu, 2022-05-19 at 19:02 +0530, Rajakavitha Kodhandapani wrote: >>> I think the INVALID index can use further explanation, in particular, from >>> my experience it seems like when building an index concurrently, the index >>> gets inserted and labeled invalid while the index is being built, and then >>> the label gets removed if it finishes successfully or gets left on the index >>> if there is a failure while building the index. It is my current >>> understanding, after experimenting, that INVALID means 'incomplete', whether >>> that's because it's in progress or because it was unable to be completed, >>> but prior to my experiment my understanding was that INVALID indicated >>> failure. >>> >>> This was especially confusing when we were adding an index to a very large >>> table because we assumed the INVALID index indicated failure when we >>> couldn't find any other sign of progress or failure. >> >> This is my first attempt at contributing to the documentation of PostgreSQL. >> Here's the patch. Please let me know if any other changes need to be made. > > Thank you! Please send patches as plain text and use bottom posting. > >> \cf3 @@ -665,11 +665,14 @@\cf5 Indexes:\ >> <para>\ >> Another caveat when building a unique index concurrently is that the\ >> uniqueness constraint is already being enforced against other >> transactions\ >> \cf6 - when the second table scan begins. This means that constraint >> violations\cf5 \ >> \cf4 + when the second table scan begins. This means that constraint >> violations\cf5 \ >> could be reported in other queries prior to the index becoming available\ >> \cf6 - for use, or even in cases where the index build eventually fails. >> Also,\cf5 \ >> \cf6 - if a failure does occur in the second scan, the >> <quote>invalid</quote> index\cf5 \ >> \cf6 - continues to enforce its uniqueness constraint afterwards.\cf5 \ >> \cf4 + for use, or even in cases where the index build eventually fails. >> The index\cf5 \ >> \cf4 + is inserted and labeled <quote>invalid</quote> while the index is >> being built,\cf5 \ >> \cf4 + and then the label is removed if the index builds successfully. If >> the index does\cf5 \ >> \cf4 + not build successfully, then the label <quote>invalid</quote> >> remains. Also, if a\cf5 \ >> } > > I don't think that this information should be added to a paragraph that > focuses on uniqueness checks in concurrent index builds. > > Actually, most of the information is already there. To quote from the page: > > If a problem arises while scanning the table, such as a deadlock or a > uniqueness violation > in a unique index, the CREATE INDEX command will fail but leave behind an > “invalid” index. > > How about the following patch to emphasize the role of "invalid": > > diff --git a/doc/src/sgml/ref/create_index.sgml > b/doc/src/sgml/ref/create_index.sgml > index d3102a87d9..fee2c61e5e 100644 > --- a/doc/src/sgml/ref/create_index.sgml > +++ b/doc/src/sgml/ref/create_index.sgml > @@ -622,7 +622,7 @@ CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT > EXISTS ] <replaceable class= > </para> > > <para> > - In a concurrent index build, the index is actually entered into > + In a concurrent index build, the index is actually entered as > <quote>invalid</quote> index into > the system catalogs in one transaction, then two table scans occur in > two more transactions. Before each table scan, the index build must > wait for existing transactions that have modified the table to terminate. > @@ -631,7 +631,7 @@ CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT > EXISTS ] <replaceable class= > scan to terminate, including transactions used by any phase of concurrent > index builds on other tables, if the indexes involved are partial or have > columns that are not simple column references. > - Then finally the index can be marked ready for use, > + Then finally the index can be marked <quote>valid</quote> and ready for > use, > and the <command>CREATE INDEX</command> command terminates. > Even then, however, the index may not be immediately usable for queries: > in the worst case, it cannot be used as long as transactions exist that > > Yours, > Laurenz Albe
