[postgis-users] Question on GIST_GEOMETRY_OPS

[strk at refractions.net]

On Tue, May 03, 2005 at 06:32:45PM -0700, Lin Jianfong wrote:
> Hello,
> 
> On section 4.5.1. GiST Indexes of PostGIS 1.0 Manual the syntax for building
> GiST index is described as follows:
> 
> CREATE INDEX [indexname] ON [tablename]
>   USING GIST ( [geometryfield] GIST_GEOMETRY_OPS)
> 
> What does GIST_GEOMETRY_OPS do?

It selects an operator class.
GiST is a general index, it requires an operator class definition
to know what to do exactly. Teoretically we could have more
than a single operator class which could be used for different
kind of accesses. Practically we have only that one.

It is defined as:

CREATE OPERATOR CLASS gist_geometry_ops
        DEFAULT FOR TYPE geometry USING gist AS ...

So I think omitting it in the CREATE INDEX command would be ok
it being the DEFAULT for GIST on geometry. Should be verified
with different pgsql versions.

--strk;

> 
> Thanks.
> 
> -- 
> Hong
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