Any spatial index support in the standard PostgreSQL installation?

I'm new to PostgreSQL.

For the default install of PostgreSQL (no extension like PostGIS), if t开发者_运维技巧here's geographic fields defined in my table, then what kinds of index does PostgreSQL support?

I didn't find any information on the spatial index in the manual.

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Use GiST, just like PostGIS uses.

But why don't you install PostGIS in your database?