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You can query the system view SYS_SPATIAL_SIMPLIFY to get information about simplified spatial geometry objects using the COPY command. When you use COPY on a shapefile, you can specify SIMPLIFY tolerance, SIMPLIFY AUTO, and SIMPLIFY AUTO max_tolerance ingestion options. The result of the simplification is summarized in SYS_SPATIAL_SIMPLIFY system view.

When SIMPLIFY AUTO max_tolerance is set, this view contains a row for each geometry that exceeded the maximum size. When SIMPLIFY tolerance is set, then one row for the entire COPY operation is stored. This row references the COPY query ID and the specified simplification tolerance.

For more information about loading a shapefile, see Loading a shapefile into Amazon Redshift.

SYS_SPATIAL_SIMPLIFY is visible to all users. Superusers can see all rows; regular users can see only their own data. For more information, see Visibility of data in system tables and views.

Table columns

Column name Data type Description
query_id bigint The ID of the query (COPY command) that generated this row.
line_number bigint When COPY SIMPLIFY AUTO option is specified, this value is the record number of the simplified record in the shapefile.
maximum_tolerance double precision The distance tolerance value specified in the COPY command. This is either the maximum tolerance value using the SIMPLIFY AUTO option, or the fixed tolerance value using the SIMPLIFY option.
initial_size bigint The size in bytes of the GEOMETRY data value before simplification.
simplified char(1) When the COPY SIMPLIFY AUTO option is specified, t if the geometry was successfully simplified, or f otherwise. The geometry might not be simplified successfully if after the simplification with the given maximum tolerance its size is still larger than the maximum geometry size.
final_size bigint When the COPY SIMPLIFY AUTO option is specified, this is the size in bytes of the geometry after simplification.
final_tolerance double precision Final tolerance chosen for the simplification.

Sample query

The following query returns the list of records that COPY simplified.

SELECT * FROM sys_spatial_simplify; query_id | line_number | maximum_tolerance | initial_size | simplified | final_size | final_tolerance ----------+-------------+-------------------+--------------+------------+------------+---------------------- 20 | 1184704 | -1 | 1513736 | t | 1008808 | 1.276386653895e-05 20 | 1664115 | -1 | 1233456 | t | 1023584 | 6.11707814796635e-06