Function cdbCopyStart

src/backend/cdb/cdbcopy.c:156–217

* starts a copy command on a specific segment database. * * may pg_throw via elog/ereport. */

 * may pg_throw via elog/ereport.
 */
void
cdbCopyStart(CdbCopy *c, CopyStmt *stmt, int file_encoding)
{
	int			flags;

	stmt = copyObject(stmt);

	/*
	 * If the output needs to be in a different encoding, tell the segment.
	 * Normally, when we run normal queries, we keep the segment connections
	 * in database encoding, and do the encoding conversions in the QD, just
	 * before sending results to the client. But in COPY TO, we don't do
	 * any conversions to the data we receive from the segments, so they
	 * must produce the output in the correct encoding.
	 *
	 * We do this by adding "ENCODING 'xxx'" option to the options list of
	 * the CopyStmt that we dispatch.
	 */
	if (file_encoding != GetDatabaseEncoding())
	{
		bool		found;
		ListCell   *option;

		/*
		 * But first check if the encoding option is already in the options
		 * list (i.e the user specified it explicitly in the COPY command)
		 */
		found = false;
		foreach(option, stmt->options)
		{
			DefElem    *defel = (DefElem *) lfirst(option);

			if (strcmp(defel->defname, "encoding") == 0)
			{
				/*
				 * The 'file_encoding' came from the options, so they should match, but
				 * let's sanity-check.
				 */
				if (pg_char_to_encoding(defGetString(defel)) != file_encoding)
					elog(ERROR, "encoding option in original COPY command does not match encoding being dispatched");
				found = true;
			}
		}

		if (!found)
		{
			const char *encname = pg_encoding_to_char(file_encoding);

			stmt->options = lappend(stmt->options,
									makeDefElem("encoding",
												(Node *) makeString(pstrdup(encname)), -1));
		}
	}

	flags = DF_WITH_SNAPSHOT | DF_CANCEL_ON_ERROR;
	if (c->copy_in)
		flags |= DF_NEED_TWO_PHASE;