ST_compress语法、参数和示例_云数据库 RDS(RDS)-阿里云帮助中心

将pcpatch对象按指定方式压缩。

语法

pcpatch ST_compress(pcpatch pc, text global_compression_schema default '', text compression_config default '');

参数

参数名称	描述
pc	pcpatch对象。
global_compression_schema	压缩框架。
compression_config	压缩配置项，指定具体维度的压缩算法。

描述

压缩框架可以为：

auto           -- determined by pcid
dimension 
laz             -- no compression config supported
ght            -- is discarded

当压缩框架为dimension时，压缩配置项可以为：

auto -- determined automatically, from values stats
zlib -- deflate compression
sigbits -- significant bits removal
rle -- run-length encoding

示例

SELECT ST_asText(ST_Compress(ST_MakePatch(1, ARRAY[-126.99,45.01,1,0, -126.98,45.02,2,0, -126.97,45.03,3,0])));

-------------------------------------------------
{"pcid":1,"pts":[
 [-126.99,45.01,1,0],[-126.98,45.02,2,0],[-126.97,45.03,3,0]
]}