Function dumpTableData_copy

src/bin/pg_dump/pg_dump.c:2307–2456

* Dump a table's contents for loading using the COPY command * - this routine is called by the Archiver when it wants the table * to be dumped. */

 *	  to be dumped.
 */
static int
dumpTableData_copy(Archive *fout, const void *dcontext)
{
	TableDataInfo *tdinfo = (TableDataInfo *) dcontext;
	TableInfo  *tbinfo = tdinfo->tdtable;
	const char *classname = tbinfo->dobj.name;
	PQExpBuffer q = createPQExpBuffer();

	/*
	 * Note: can't use getThreadLocalPQExpBuffer() here, we're calling fmtId
	 * which uses it already.
	 */
	PQExpBuffer clistBuf = createPQExpBuffer();
	PGconn	   *conn = GetConnection(fout);
	PGresult   *res;
	int			ret;
	char	   *copybuf;
	const char *column_list;

	pg_log_info("dumping contents of table \"%s.%s\"",
				tbinfo->dobj.namespace->dobj.name, classname);

	/*
	 * Specify the column list explicitly so that we have no possibility of
	 * retrieving data in the wrong column order.  (The default column
	 * ordering of COPY will not be what we want in certain corner cases
	 * involving ADD COLUMN and inheritance.)
	 */
	column_list = fmtCopyColumnList(tbinfo, clistBuf);

	/*
	 * Use COPY (SELECT ...) TO when dumping a foreign table's data, and when
	 * a filter condition was specified.  For other cases a simple COPY
	 * suffices.
	 */
	if (tdinfo->filtercond || tbinfo->relkind == RELKIND_FOREIGN_TABLE)
	{
		appendPQExpBufferStr(q, "COPY (SELECT ");
		/* klugery to get rid of parens in column list */
		if (strlen(column_list) > 2)
		{
			appendPQExpBufferStr(q, column_list + 1);
			q->data[q->len - 1] = ' ';
		}
		else
			appendPQExpBufferStr(q, "* ");

		appendPQExpBuffer(q, "FROM %s %s) TO stdout;",
						  fmtQualifiedDumpable(tbinfo),
						  tdinfo->filtercond ? tdinfo->filtercond : "");
	}
	else
	{
		appendPQExpBuffer(q, "COPY %s %s TO stdout;",
						  fmtQualifiedDumpable(tbinfo),
						  column_list);
	}
	res = ExecuteSqlQuery(fout, q->data, PGRES_COPY_OUT);