Add postgis

Author: huanglii

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+---
+comments: true
+tags:
+  - GIS
+---
+
+# PostGIS
+
+## 安装
+
+```sql
+CREATE SCHEMA postgis;
+GRANT USAGE ON schema postgis to public;
+
+CREATE EXTENSION postgis SCHEMA postgis;
+CREATE EXTENSION postgis_raster SCHEMA postgis;
+
+ALTER DATABASE postgis_in_action SET search_path=public,postgis,contrib;
+```
+
+!!! info "提示"
+    虽然不是必需的，但建议在单独的模式（如 postgis）中安装 postgis，这样函数就不会弄乱默认的公共模式。