Thread: When (and whether) should we improve the chapter on parallel query to accommodate parallel data updates?
When (and whether) should we improve the chapter on parallel query to accommodate parallel data updates?
From
"tsunakawa.takay@fujitsu.com"
Date:
Hello, While I'm reviewing patches for parallel operations, it occured to me that we may need to correct the words and enrich contentin "15. Parallel Query". I don't have a concrete image of how the content should be yet, and I think the documentationmay be improved after the feature freeze (i.e. April.) Is anyone already doing this kind of modifications? First, as parallel data updates are being introduced, the chapter title "Parallel Query" should be changed to "Parallel Execution"or "Parallel Operation". It's confusing to see that Postgres uses "query" to also mean statements other than SELECT,but the SQL standard seems to differentiate them; SELECT is explained in "7 Query expressions" and INSERT/DELETE/UPDATEetc. are described in "14 Data manipulation". Following the SQL standard, Postgres manual have separatechapters "6. Data Manipulation" and "7. Queries". (e.g. query plan in EXPLAIN should have been execution plan? But it's too late now.) The chapter content should also be changed to use appropriate words carefully. FYI, Oracle wisely give the chapter title "8 Using Parallel Execution" [1]. SQL Server isn't very clear, but it seems thatit doesn't use "query" for INSERT, like in "The TABLOCK hint can enable parallel insert operations." [2] [3] Second, I expected to see descriptions in "15. Parallel Query" that there are other (recently added) parallel operationssuch as parallel index build and parallel VACUUM, but I didn't find them. Also, I couldn't find information onparallelism in possible chapters such as "11. Indexes" or "25. Routine Database Maintenance Tasks". Where can users noticethat they can parallelize and speed up those operations? Only in reference pages? I think it's better to have thosedescriptions in the Parallel Query chapter. If nobody hasn't started making this kind of modifications, can we deter it after the feature freeze? Or should people involvedin developing parallel features cooperate to revise the manual as part of their patches? Regards Takayuki Tsunakawa [1] 8 Using Parallel Execution https://docs.oracle.com/en/database/oracle/oracle-database/21/vldbg/using-parallel.html#GUID-3E2AE088-2505-465E-A8B2-AC38813EA355 [2] Query Processing Architecture Guide https://docs.microsoft.com/en-us/sql/relational-databases/query-processing-architecture-guide?view=sql-server-ver15 [3] INSERT (Transact-SQL) https://docs.microsoft.com/en-us/sql/t-sql/statements/insert-transact-sql?view=sql-server-ver15#best-practices Regards Takayuki Tsunakawa
Re: When (and whether) should we improve the chapter on parallel query to accommodate parallel data updates?
From
Amit Kapila
Date:
On Wed, Jan 6, 2021 at 12:13 PM tsunakawa.takay@fujitsu.com <tsunakawa.takay@fujitsu.com> wrote: > > Second, I expected to see descriptions in "15. Parallel Query" that there are other (recently added) parallel operationssuch as parallel index build and parallel VACUUM, but I didn't find them. Also, I couldn't find information onparallelism in possible chapters such as "11. Indexes" or "25. Routine Database Maintenance Tasks". Where can users noticethat they can parallelize and speed up those operations? Only in reference pages? I think it's better to have thosedescriptions in the Parallel Query chapter. > I think it is in the respective pages of those operations. Forex. the information about parallel vacuum can be found in the Vacuum page [1]. > If nobody hasn't started making this kind of modifications, can we deter it after the feature freeze? Or should peopleinvolved in developing parallel features cooperate to revise the manual as part of their patches? > I think each feature should develop the docs as part of feature development but if we want to see some additional work like improving overall docs for parallel execution as you are suggesting then it can be done separately as well. I think you have a valid point but maybe it would be better to do the improvements you are suggesting once the parallel inserts related work is committed. [1] - https://www.postgresql.org/docs/devel/sql-vacuum.html -- With Regards, Amit Kapila.
RE: When (and whether) should we improve the chapter on parallel query to accommodate parallel data updates?
From
"tsunakawa.takay@fujitsu.com"
Date:
From: Amit Kapila <amit.kapila16@gmail.com> > I think each feature should develop the docs as part of feature > development but if we want to see some additional work like improving > overall docs for parallel execution as you are suggesting then it can > be done separately as well. > > I think you have a valid point but maybe it would be better to do the > improvements you are suggesting once the parallel inserts related work > is committed. OK. I think at least the words query, statement, execution, and/or operation should be used appropriately before RC (ideally,before beta). Maybe parallel copy should also be put in the chapter. Anyway, I agree that each developer focuseson their features for the moment (parallel insert select, parallel copy, parallel CTAS, etc), and then make the documentationconsistent and well-organized after they've settled. (I just felt a bit uneasy to say "this patch looks good"while leaving the document consistency.) Regards Takayuki Tsunakawa