Postgres-如何在插入上自动调用ST_SetSRID(ST_MakePoint(lng,lat),4326)? [英] Postgres - How to automatically call ST_SetSRID(ST_MakePoint(lng, lat), 4326) on inserts?
问题描述
我正在使用postGIS,但对SQL不太熟悉.
I'm using postGIS, and I'm not very familiar with SQL.
只要执行以下操作( pseudocode!),我就可以成功地插入到markers
表中:
I can successfully insert into my markers
table as long as I do something like this (pseudocode!):
'INSERT INTO markers(created_by, title, description, lat, lng, geography)\
values($1, $2, $3, $4::decimal, $5::decimal, ST_SetSRID(ST_MakePoint($5::decimal, $4::decimal), $6))',
[
data.created_by,
data.title,
data.description,
data.lat,
data.lng,
4326
]'
如您所见,我正在从我的应用程序代码中执行ST_SetSRID(ST_MakePoint($5::decimal, $4::decimal), $6)
.
As you can see, I am doing ST_SetSRID(ST_MakePoint($5::decimal, $4::decimal), $6)
from my application code.
我想避免这种情况,而是将其放在数据库端.由于我可以在数据库端执行自动时间戳记之类的操作,因此我想知道是否还可以在表本身上执行ST_SetSRID(ST_MakePoint(lng, lat), 4326)
.
I want to avoid that, and instead put this on the database side. Since I can do things like auto time stamps on the db side, I'm wondering if I can also do ST_SetSRID(ST_MakePoint(lng, lat), 4326)
on the table itself.
这样,应用程序只需要提供lat和lng,数据库就会执行ST_SetSRID(ST_MakePoint())
操作.
This way, the application only needs to provide lat and lng, and the database will do the ST_SetSRID(ST_MakePoint())
operation.
谢谢
我不确定谁将答案标记为+1,因为两者都提供了非常好的帮助和建议.我希望未来的读者能读懂它们,并希望能学到一些东西!
I'm not sure whose answer to mark as +1 since both offered tremendously good help and advice. I hope future readers will read both and hopefully learn something!
推荐答案
您可以通过使用触发器来做到这一点.您的插入调用将不处理几何图形,仅处理纬度和其他非空间字段,并且触发函数将创建几何图形.让我们不要忘记在更新行时执行相同的操作.
请注意,我已经对SRID进行了硬编码,因为不可能将额外的动态参数传递给触发函数.如果需要,在表中添加一个字段来保存该值,您可以将其称为new.srid
You can do this by using a trigger. Your insert call would not deal with the geometry, only with lat-long and other non-spatial fields, and the trigger function will create the geometry. Let's not forget to do the same when updating the row.
Note that I have hard-coded the SRID as it is not possible to pass extra dynamic parameters to the trigger function. If need be, add a field to your table to hold this value and you can refer to it as new.srid
CREATE OR REPLACE FUNCTION markers_geog_tg_fn() RETURNS trigger AS
$BODY$BEGIN
IF TG_OP = 'INSERT' AND (NEW.lat ISNULL or NEW.lng ISNULL ) THEN
RETURN NEW; -- no geometry
ELSIF TG_OP = 'UPDATE' THEN
--Lat Long updated to null, erase geometry
IF NEW.lat ISNULL or NEW.lng ISNULL THEN
NEW.geography = NULL;
END IF;
IF NEW.lat IS NOT DISTINCT FROM OLD.lat and NEW.lng IS NOT DISTINCT FROM OLD.lng THEN
RETURN NEW; -- same old geometry
END IF;
END IF;
-- Attempt to transform a geometry
BEGIN
NEW.geography := ST_SetSRID(ST_MakePoint(NEW.lng::decimal, NEW.lat::decimal), 4326))
EXCEPTION WHEN SQLSTATE 'XX000' THEN
RAISE WARNING 'geography not updated: %', SQLERRM;
END;
RETURN NEW;
END;$BODY$ LANGUAGE plpgsql;
CREATE TRIGGER markers_geog_tg BEFORE INSERT OR UPDATE
ON markers FOR EACH ROW
EXECUTE PROCEDURE markers_geog_tg_fn();
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