Function MangleCopyFileName

src/backend/commands/copy.c:1197–1227

* Modify the filename in cstate->filename, and cstate->cdbsreh if any, * for COPY ON SEGMENT. * * Replaces the " " token in the filename with this segment's ID. */

 * Replaces the "<SEGID>" token in the filename with this segment's ID.
 */
void
MangleCopyFileName(char **filenameptr, CdbSreh *cdbsreh)
{
	Assert(filenameptr && *filenameptr);

	char	   *filename = *filenameptr;
	StringInfoData filepath;

	initStringInfo(&filepath);
	appendStringInfoString(&filepath, filename);

	replaceStringInfoString(&filepath, "<SEG_DATA_DIR>", DataDir);

	if (strstr(filename, "<SEGID>") == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("<SEGID> is required for file name")));

	char segid_buf[8];
	snprintf(segid_buf, 8, "%d", GpIdentity.segindex);
	replaceStringInfoString(&filepath, "<SEGID>", segid_buf);

	*filenameptr = filepath.data;
	/* Rename filename if error log needed */
	if (NULL != cdbsreh)
	{
		snprintf(cdbsreh->filename,
				 sizeof(cdbsreh->filename), "%s",
				 filepath.data);
	}
}

static uint64
CopyToQueryOnSegment(CopyToState cstate)