基于jdbc实现pg流式查询

驱动版本：postgresql-42.3.8

满足条件

1. fetchSize > 0
2. !connection.getAutoCommit()=true
3. 其他默认

实现代码

autoCommit=false
fetchSize>0
即可实现流式查询

public static void executeSqlByStream(Connection conn, String sql, Boolean autoCommit, Integer fetchSize, ResultStreamHandler<Map> callbackTask) {
        AssertUtils.notBlank(sql, "execute sql can't be null.");
        List<Map<String, Object>> result = Lists.newArrayList();
        ResultSet res = null;
        Statement statement = null;
        Map<String, Object> ROW = Maps.newLinkedHashMap();
        try {
            conn.setAutoCommit(autoCommit);
            statement = conn.createStatement();
            statement.setFetchSize(fetchSize);
            if (statement.execute(sql)) {
                res = statement.getResultSet();
                int columns = res.getMetaData().getColumnCount();
                List<String> columnName = Lists.newArrayList();
                for (int i = 0; i < columns; i++) {
                    columnName.add(res.getMetaData().getColumnLabel(i + 1));
                }

                while (res.next()) {
					
                   	// 将数据处理，存入ROW
                   	
					// 回调-数据处理
                    callbackTask.handleResult(ROW);
                }
            }
        } catch (Exception e) {
            throw new ServiceException(String.format("SQL select exception：%s", e.getMessage()), e);
        } finally {
            try {
                    conn.setAutoCommit(true);
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            closeDBResources(res, statement, null);
        }
    }