Horton

RE: Parallel copy

Hou, Zhijie <houzj.fnst@cn.fujitsu.com>

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From: "Hou, Zhijie" <houzj.fnst@cn.fujitsu.com>
To: vignesh C <vignesh21@gmail.com>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Rafia Sabih <rafia.pghackers@gmail.com>, Ashutosh Sharma <ashu.coek88@gmail.com>, "Andres Freund" <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, Ants Aasma <ants@cybertec.at>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, "Alastair Turner" <minion@decodable.me>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Amit Kapila <amit.kapila16@gmail.com>
Date: 2020-10-18T02:17:07Z
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. Allow WaitLatch() to be used without a latch.

  2. Add %P to log_line_prefix for parallel group leader

  3. Include replication origins in SQL functions for commit timestamp

  4. Avoid useless buffer allocations during binary COPY FROM.

Hi Vignesh,

After having a look over the patch,
I have some suggestions for 
0003-Allow-copy-from-command-to-process-data-from-file.patch.

1.

+static uint32
+EstimateCstateSize(ParallelContext *pcxt, CopyState cstate, List *attnamelist,
+				   char **whereClauseStr, char **rangeTableStr,
+				   char **attnameListStr, char **notnullListStr,
+				   char **nullListStr, char **convertListStr)
+{
+	uint32		strsize = MAXALIGN(sizeof(SerializedParallelCopyState));
+
+	strsize += EstimateStringSize(cstate->null_print);
+	strsize += EstimateStringSize(cstate->delim);
+	strsize += EstimateStringSize(cstate->quote);
+	strsize += EstimateStringSize(cstate->escape);


It use function EstimateStringSize to get the strlen of null_print, delim, quote and escape.
But the length of null_print seems has been stored in null_print_len.
And delim/quote/escape must be 1 byte, so I think call strlen again seems unnecessary.

How about  " strsize += sizeof(uint32) + cstate->null_print_len + 1"

2.
+	strsize += EstimateNodeSize(cstate->whereClause, whereClauseStr);

+	copiedsize += CopyStringToSharedMemory(cstate, whereClauseStr,
+										   shmptr + copiedsize);

Some string length is counted for two times.
The ' whereClauseStr ' has call strlen in EstimateNodeSize once and call strlen in CopyStringToSharedMemory again.
I don't know wheather it's worth to refacor the code to avoid duplicate strlen . what do you think ?

Best regards,
houzj