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69 lines
3.2 KiB
69 lines
3.2 KiB
CartoDB User Table
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==================
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Introduction
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----------
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A CartoDB user table is a table with a well-known set of columns and a well-known set of triggers attached on.
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Columns
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----------
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The required columns of a CartoDB table are:
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- ``cartodb_id``
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- This column will be used as the primary key of the table and it has a sequence as default value
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- Its values must be integer, non-zero, non-null and unique
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- B-Tree indexed
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- ``the_geom``
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- This column stores the main geometric features of a table
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- The type of the column in the Postgres database is ``geometry(Geometry,4326)```
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- GiST indexed
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- geometry, GiST indexed, constrained (see below)
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- ``the_geom_webmercator``
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- This column stores the geometries used for rendering purposes
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- The type of the column in the Postgres database is ``geometry(Geometry,3857)``
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- GiST indexed
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- This column is automatically updated by the system when the ``the_geom`` column is updated or when there is an insertion of a new row into the table (See triggers below)
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The values of ``the_geom`` and ``the_geom_webmercator`` must be two-dimensional Points, MultiLineStrings or MultiPolygons. Different geometric types in a CartoDB table are not supported.
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Described table example
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^^^^^^^^^^
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::
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Column | Type | Modifiers
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----------------------+-------------------------+--------------------------------------------------------
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cartodb_id | bigint | not null default nextval('t_cartodb_id_seq'::regclass)
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the_geom | geometry(Geometry,4326) |
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the_geom_webmercator | geometry(Geometry,3857) |
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Indexes:
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"table_name_pkey" PRIMARY KEY, btree (cartodb_id)
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"table_name_the_geom_idx" gist (the_geom)
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"table_name_the_geom_webmercator_idx" gist (the_geom_webmercator)
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Triggers
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----------
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The triggers generated in each CartoDB table are:
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- ``track_updates`` after modifying statement updates ``cdb_tablemetadata``
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- ``test_quota`` before changing statement to forbid if overquota
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- ``test_quota_per_row`` before insert ot update row to forbid if overquota (checked on a probabilistic basis)
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- ``update_the_geom_webmercator`` before insert or update row to maintain the ``the_geom_webmercator`` updated with the contents in ``the_geom``
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Described triggers example
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^^^^^^^^^^
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::
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test_quota BEFORE INSERT OR UPDATE ON t FOR EACH STATEMENT EXECUTE PROCEDURE cdb_checkquota('0.1', '-1', 'public')
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test_quota_per_row BEFORE INSERT OR UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE cdb_checkquota('0.001', '-1', 'public')
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track_updates AFTER INSERT OR DELETE OR UPDATE OR TRUNCATE ON t FOR EACH STATEMENT EXECUTE PROCEDURE cdb_tablemetadata_trigger()
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update_the_geom_webmercator_trigger BEFORE INSERT OR UPDATE OF the_geom ON t FOR EACH ROW EXECUTE PROCEDURE _cdb_update_the_geom_webmercator()
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Further details
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----------
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Some conversions will be attempted to perform upon cartodbfication when certain fields appear:
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- ``cartodb_id``: If found type TEXT will be attempted to cast to integer. If not casteable, an eror will be raised.
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- ``the_geom``: If found type TEXT will be attempted to cast to geometry(Geometry,4326).
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