【解决办法】
pg数据库里时间戳是秒级的,而js端时间获取时间戳是毫秒级的,且需注意pg里的是否带时区8小时。用to_timestamp函数将秒级的时间戳转换为时间即可过滤,完整示例:
http://localhost:8090/iserver/services/map-pgis/arcgisrest/liuda@mvtTestDB/MapServer/export?bbox=94.072,34.444,98.530,37.158&layerDefs={"0":"mytime>to_timestamp(1639738455)"}