37 lines
1023 B
PL/PgSQL
37 lines
1023 B
PL/PgSQL
-- Maximum supported zoom level
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CREATE OR REPLACE FUNCTION _CDB_MaxSupportedZoom()
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RETURNS int
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LANGUAGE SQL
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IMMUTABLE
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AS $$
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-- The maximum zoom level has to be limited for various reasons,
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-- e.g. zoom levels greater than 31 would require tile coordinates
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-- that would not fit in an INTEGER (which is signed, 32 bits long).
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-- We'll choose 20 as a limit which is safe also when the JavaScript shift
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-- operator (<<) is used for computing powers of two.
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SELECT 29;
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$$;
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CREATE OR REPLACE FUNCTION cartodb.CDB_ZoomFromScale(scaleDenominator numeric)
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RETURNS int
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LANGUAGE SQL
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IMMUTABLE
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AS $$
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SELECT
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CASE
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WHEN scaleDenominator > 600000000 THEN
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-- Scale is smaller than zoom level 0
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NULL
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WHEN scaleDenominator = 0 THEN
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-- Actual zoom level would be infinite
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_CDB_MaxSupportedZoom()
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ELSE
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CAST (
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LEAST(
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ROUND(LOG(2, 559082264.028/scaleDenominator)),
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_CDB_MaxSupportedZoom()
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)
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AS INTEGER)
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END;
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$$;
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