Horton

Re: Early WIP/PoC for inlining CTEs

Andreas Karlsson <andreas@proxel.se>

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From: Andreas Karlsson <andreas@proxel.se>
To: Andrew Gierth <andrew@tao11.riddles.org.uk>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, David Fetter <david@fetter.org>, Thomas Munro <thomas.munro@enterprisedb.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2019-01-02T04:29:16Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Prevent inlining of multiply-referenced CTEs with outer recursive refs.

  2. Allow user control of CTE materialization, and change the default behavior.

  3. Split QTW_EXAMINE_RTES flag into QTW_EXAMINE_RTES_BEFORE/_AFTER.

  4. document when PREPARE uses generic plans

On 1/1/19 3:18 AM, Andrew Gierth wrote:
> I had a comment around here which seems to have been lost:
> 
>   * Secondly, views (and explicit subqueries) currently have
>   * different behaviour w.r.t. SELECT FOR UPDATE than CTEs do. A
>   * FOR UPDATE clause is treated as extending into views and
>   * subqueries, but not into CTEs. We preserve this distinction
>   * by not trying to push rowmarks into the new subquery.
> 
> This comment seems to me to be worth preserving (unless this behavior is
> changed). What I'm referring to is the following, which is unchanged by
> the patch:
> 
> create table t1 as select 123 as a;
> create view v1 as select * from t1;
> select * from t1 for update;  -- locks row in t1
> select * from t1 for update of t1;  -- locks row in t1
> select * from v1 for update;  -- locks row in t1
> select * from v1 for update of v1;  -- locks row in t1
> select * from (select * from t1) s1 for update;  -- locks row in t1
> select * from (select * from t1) s1 for update of s1;  -- locks row in t1
> with c1 as (select * from t1)
>    select * from c1 for update;  -- does NOT lock anything at all
> with c1 as (select * from t1)
>    select * from c1 for update of c1;  -- parse-time error
> 
> (Obviously, inlining decisions should not change what gets locked;
> the behavior here should not be changed unless it is changed for both
> inlined and non-inlined CTEs.)

I see, I misread the comment. I will re-add it, possibly with some word 
smithing. Thanks!

Andreas