RE: Parallel Inserts in CREATE TABLE AS - Mailing list pgsql-hackers

From Hou, Zhijie
Subject RE: Parallel Inserts in CREATE TABLE AS
Date
Msg-id f12c78d9c1b04cb081b371919da8d27c@G08CNEXMBPEKD05.g08.fujitsu.local
Whole thread Raw
In response to Re: Parallel Inserts in CREATE TABLE AS  (Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>)
Responses Re: Parallel Inserts in CREATE TABLE AS  (Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>)
List pgsql-hackers
> > For v20-0001-Parallel-Inserts-in-CREATE-TABLE-AS.patch :
> >
> > ParallelInsCmdEstimate :
> >
> > +   Assert(pcxt && ins_info &&
> > +          (ins_cmd == PARALLEL_INSERT_CMD_CREATE_TABLE_AS));
> > +
> > +   if (ins_cmd == PARALLEL_INSERT_CMD_CREATE_TABLE_AS)
> >
> > Sinc the if condition is covered by the assertion, I wonder why the if
> check is still needed.
> >
> > Similar comment for SaveParallelInsCmdFixedInfo and
> > SaveParallelInsCmdInfo
> 
> Thanks.
> 
> The idea is to have assertion with all the expected ins_cmd types, and then
> later to have selective handling for different ins_cmds. For example, if
> we add (in future) parallel insertion in Refresh Materialized View, then
> the code in those functions will be something
> like:
> 
> +static void
> +ParallelInsCmdEstimate(ParallelContext *pcxt, ParallelInsertCmdKind
> ins_cmd,
> +                       void *ins_info)
> +{
> +    Assert(pcxt && ins_info &&
> +           (ins_cmd == PARALLEL_INSERT_CMD_CREATE_TABLE_AS ||
> +            (ins_cmd == PARALLEL_INSERT_CMD_REFRESH_MAT_VIEW));
> +
> +    if (ins_cmd == PARALLEL_INSERT_CMD_CREATE_TABLE_AS)
> +    {
> +
> +    }
> +   else if (ns_cmd == PARALLEL_INSERT_CMD_REFRESH_MAT_VIEW)
> +   {
> +
> +   }
> 
> Similarly for other functions as well.

I think it makes sense.

And if the check about ' ins_cmd == xxx1 || ins_cmd == xxx2' may be used in some places,
How about define a generic function with some comment to mention the purpose.

An example in INSERT INTO SELECT patch:
+/*
+ * IsModifySupportedInParallelMode
+ *
+ * Indicates whether execution of the specified table-modification command
+ * (INSERT/UPDATE/DELETE) in parallel-mode is supported, subject to certain
+ * parallel-safety conditions.
+ */
+static inline bool
+IsModifySupportedInParallelMode(CmdType commandType)
+{
+    /* Currently only INSERT is supported */
+    return (commandType == CMD_INSERT);
+}

Best regards,
houzj



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