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Merge pull request #221 from CartoDB/219-overviews-tolerance

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New function CDB_CreateOverviewsWithToleranceInPixels
This commit is contained in:
Javier Goizueta
2016-04-05 14:01:25 +02:00
parent c6885c2972 06bb669d4c
commit 16a58c479d
4 changed files with 63 additions and 28 deletions
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7
doc/CDB_Overviews.md
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@@ -48,6 +48,13 @@ CDB_CreateOverviews(table_name, ref_z_strategy, reduction_strategy)
- **base_z** integer, base Z level assigned to the base table.
- **overview_z** integer, Z level for which to generate the overview.
#### Tolerance / level of detail
The level of detail to be representable by each overview layer can
be specified as a tolerance in pixels (if different from the default of 2 pixels)
with the function `CDB_CreateOverviewsWithToleranceInPixels`
which has as a second additional argument the desired tolerance.
### CDB_Overviews
Obtain overview metadata for a given table (existing overviews).

47
scripts-available/CDB_Overviews.sql
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@@ -291,15 +291,21 @@ $$ LANGUAGE PLPGSQL STABLE;
-- Parameters:
-- reloid: oid of the input table. It must be a cartodbfy'ed table.
-- Return value: Z level as an integer
CREATE OR REPLACE FUNCTION _CDB_Feature_Density_Ref_Z_Strategy(reloid REGCLASS)
CREATE OR REPLACE FUNCTION _CDB_Feature_Density_Ref_Z_Strategy(reloid REGCLASS, tolerance_px FLOAT8 DEFAULT NULL)
RETURNS INTEGER
AS $$
DECLARE
lim FLOAT8 := 500; -- TODO: determine/parameterize this
lim FLOAT8;
nz integer := 4;
fd FLOAT8;
c FLOAT8;
BEGIN
IF (tolerance_px IS NULL) OR tolerance_px = 0 THEN
lim := 500;
ELSE
lim := floor(power(256/tolerance_px, 2))/2;
END IF;
-- Compute fd as an estimation of the (maximum) number
-- of features per unit of tile area (in webmercator squared meters)
SELECT _CDB_Feature_Density(reloid, nz) INTO fd;
@@ -346,7 +352,7 @@ $$ LANGUAGE PLPGSQL IMMUTABLE;
-- ref_z Z level assigned to the original table
-- overview_z Z level of the overview to be generated, must be smaller than ref_z
-- Return value: Name of the generated overview table
CREATE OR REPLACE FUNCTION _CDB_Sampling_Reduce_Strategy(reloid REGCLASS, ref_z INTEGER, overview_z INTEGER)
CREATE OR REPLACE FUNCTION _CDB_Sampling_Reduce_Strategy(reloid REGCLASS, ref_z INTEGER, overview_z INTEGER, tolerance_px FLOAT8 DEFAULT NULL)
RETURNS REGCLASS
AS $$
DECLARE
@@ -359,6 +365,7 @@ AS $$
table_name TEXT;
BEGIN
overview_rel := _CDB_Overview_Name(reloid, ref_z, overview_z);
-- TODO: compute fraction from tolerance_px if not NULL
fraction := power(2, 2*(overview_z - ref_z));
SELECT * FROM _cdb_split_table_name(reloid) INTO schema_name, table_name;
@@ -575,14 +582,13 @@ $$ LANGUAGE PLPGSQL STABLE;
-- ref_z Z level assigned to the original table
-- overview_z Z level of the overview to be generated, must be smaller than ref_z
-- Return value: Name of the generated overview table
CREATE OR REPLACE FUNCTION _CDB_GridCluster_Reduce_Strategy(reloid REGCLASS, ref_z INTEGER, overview_z INTEGER)
CREATE OR REPLACE FUNCTION _CDB_GridCluster_Reduce_Strategy(reloid REGCLASS, ref_z INTEGER, overview_z INTEGER, grid_px FLOAT8 DEFAULT NULL)
RETURNS REGCLASS
AS $$
DECLARE
overview_rel TEXT;
reduction FLOAT8;
base_name TEXT;
grid_px FLOAT8 = 7.5; -- Grid size in pixels at Z level overview_z
grid_m FLOAT8;
aggr_attributes TEXT;
attributes TEXT;
@@ -602,6 +608,11 @@ AS $$
overview_rel := _CDB_Overview_Name(reloid, ref_z, overview_z);
-- Grid size in pixels at Z level overview_z
IF grid_px IS NULL THEN
grid_px := 7.5;
END IF;
SELECT * FROM _cdb_split_table_name(reloid) INTO schema_name, table_name;
-- compute grid cell size using the overview_z dimension...
@@ -675,7 +686,20 @@ $$ LANGUAGE PLPGSQL;
-- created by the strategy must have the same columns
-- as the base table and in the same order.
-- Return value: Array with the names of the generated overview tables
CREATE OR REPLACE FUNCTION CDB_CreateOverviews(reloid REGCLASS, refscale_strategy regproc DEFAULT '_CDB_Feature_Density_Ref_Z_Strategy'::regproc, reduce_strategy regproc DEFAULT '_CDB_GridCluster_Reduce_Strategy'::regproc)
CREATE OR REPLACE FUNCTION CDB_CreateOverviews(reloid REGCLASS, refscale_strategy regproc DEFAULT '_CDB_Feature_Density_Ref_Z_Strategy(REGCLASS,FLOAT8)'::regprocedure, reduce_strategy regproc DEFAULT '_CDB_GridCluster_Reduce_Strategy(REGCLASS,INTEGER,INTEGER,FLOAT8)'::regprocedure)
RETURNS text[]
AS $$
DECLARE
tolerance_px FLOAT8;
BEGIN
-- Use the default tolerance
tolerance_px := 2.0;
RETURN CDB_CreateOverviewsWithToleranceInPixels(reloid, tolerance_px, refscale_strategy, reduce_strategy);
END;
$$ LANGUAGE PLPGSQL;
-- Create overviews with additional parameter to define the desired detail/tolerance in pixels
CREATE OR REPLACE FUNCTION CDB_CreateOverviewsWithToleranceInPixels(reloid REGCLASS, tolerance_px FLOAT8, refscale_strategy regproc DEFAULT '_CDB_Feature_Density_Ref_Z_Strategy(REGCLASS,FLOAT8)'::regprocedure, reduce_strategy regproc DEFAULT '_CDB_GridCluster_Reduce_Strategy(REGCLASS,INTEGER,INTEGER,FLOAT8)'::regprocedure)
RETURNS text[]
AS $$
DECLARE
@@ -688,7 +712,7 @@ DECLARE
overviews_step integer := 1;
BEGIN
-- Determine the referece zoom level
EXECUTE 'SELECT ' || quote_ident(refscale_strategy::text) || Format('(''%s'');', reloid) INTO ref_z;
EXECUTE 'SELECT ' || quote_ident(refscale_strategy::text) || Format('(''%s'', %s);', reloid, tolerance_px) INTO ref_z;
-- Determine overlay zoom levels
-- TODO: should be handled by the refscale_strategy?
@@ -702,7 +726,7 @@ BEGIN
base_z := ref_z;
base_rel := reloid;
FOREACH overview_z IN ARRAY overviews_z LOOP
EXECUTE 'SELECT ' || quote_ident(reduce_strategy::text) || Format('(''%s'', %s, %s);', base_rel, base_z, overview_z) INTO base_rel;
EXECUTE 'SELECT ' || quote_ident(reduce_strategy::text) || Format('(''%s'', %s, %s, %s);', base_rel, base_z, overview_z, tolerance_px) INTO base_rel;
IF base_rel IS NULL THEN
EXIT;
END IF;
@@ -714,3 +738,10 @@ BEGIN
RETURN overview_tables;
END;
$$ LANGUAGE PLPGSQL;
-- Here are some older signatures of these functions, no longar in use.
-- They must be droped here, after the (new) definition of the function `CDB_CreateOverviews`
-- because that function used to contain references to them in the default argument values.
DROP FUNCTION IF EXISTS _CDB_Feature_Density_Ref_Z_Strategy(REGCLASS);
DROP FUNCTION IF EXISTS _CDB_GridCluster_Reduce_Strategy(REGCLASS,INTEGER,INTEGER);
DROP FUNCTION IF EXISTS _CDB_Sampling_Reduce_Strategy(REGCLASS,INTEGER,INTEGER);

10
test/CDB_OverviewsTest.sql
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@@ -8,7 +8,7 @@ SELECT _CDB_Aggregated_Attributes_Expression('base_bare_t'::regclass);
SELECT _CDB_Aggregated_Attributes_Expression('base_bare_t'::regclass, 'tab');
SELECT CDB_CreateOverviews('base_bare_t'::regclass);
SELECT count(*) FROM _vovw_5_base_bare_t;
SELECT count(*) FROM _vovw_2_base_bare_t;
SELECT _CDB_Aggregable_Attributes_Expression('base_t'::regclass);
@@ -16,7 +16,7 @@ SELECT _CDB_Aggregated_Attributes_Expression('base_t'::regclass);
SELECT _CDB_Aggregated_Attributes_Expression('base_t'::regclass, 'tab');
SELECT CDB_CreateOverviews('base_t'::regclass);
SELECT count(*) FROM _vovw_5_base_t;
SELECT count(*) FROM _vovw_2_base_t;
SELECT CDB_CreateOverviews('polyg_t'::regclass);
@@ -31,7 +31,11 @@ SELECT CDB_Overviews('column_types_t'::regclass);
SELECT CDB_DropOverviews('column_types_t'::regclass);
SELECT CDB_DropOverviews('base_bare_t'::regclass);
SELECT CDB_DropOverviews('base_t'::regclass);
SELECT count(*) FROM _vovw_5_base_t;
SELECT count(*) FROM _vovw_2_base_t;
SELECT CDB_CreateOverviewsWithToleranceInPixels('base_t'::regclass, 7.5);
SELECT count(*) FROM _vovw_2_base_t;
SELECT CDB_DropOverviews('base_t'::regclass);
DROP TABLE column_types_t;
DROP TABLE base_bare_t;

27
test/CDB_OverviewsTest_expect
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@@ -9,51 +9,44 @@ SELECT 1114
{_vovw_5_base_bare_t,_vovw_4_base_bare_t,_vovw_3_base_bare_t,_vovw_2_base_bare_t,_vovw_1_base_bare_t,_vovw_0_base_bare_t}
125
{_vovw_3_base_bare_t,_vovw_2_base_bare_t,_vovw_1_base_bare_t,_vovw_0_base_bare_t}
113
number,int_number,name,start
AVG(number)::double precision AS number,AVG(int_number)::integer AS int_number,CASE count(*) WHEN 1 THEN MIN(name) ELSE NULL END::text AS name,CASE count(*) WHEN 1 THEN MIN(start) ELSE NULL END::date AS start
AVG(tab.number)::double precision AS number,AVG(tab.int_number)::integer AS int_number,CASE count(*) WHEN 1 THEN MIN(tab.name) ELSE NULL END::text AS name,CASE count(*) WHEN 1 THEN MIN(tab.start) ELSE NULL END::date AS start
{_vovw_5_base_t,_vovw_4_base_t,_vovw_3_base_t,_vovw_2_base_t,_vovw_1_base_t,_vovw_0_base_t}
125
{_vovw_3_base_t,_vovw_2_base_t,_vovw_1_base_t,_vovw_0_base_t}
113
{_vovw_5_column_types_t,_vovw_4_column_types_t,_vovw_3_column_types_t,_vovw_2_column_types_t,_vovw_1_column_types_t,_vovw_0_column_types_t}
{_vovw_3_column_types_t,_vovw_2_column_types_t,_vovw_1_column_types_t,_vovw_0_column_types_t}
(base_t,0,_vovw_0_base_t)
(base_t,1,_vovw_1_base_t)
(base_t,2,_vovw_2_base_t)
(base_t,3,_vovw_3_base_t)
(base_t,4,_vovw_4_base_t)
(base_t,5,_vovw_5_base_t)
(base_t,0,_vovw_0_base_t)
(base_t,1,_vovw_1_base_t)
(base_t,2,_vovw_2_base_t)
(base_t,3,_vovw_3_base_t)
(base_t,4,_vovw_4_base_t)
(base_t,5,_vovw_5_base_t)
(base_bare_t,0,_vovw_0_base_bare_t)
(base_bare_t,1,_vovw_1_base_bare_t)
(base_bare_t,2,_vovw_2_base_bare_t)
(base_bare_t,3,_vovw_3_base_bare_t)
(base_bare_t,4,_vovw_4_base_bare_t)
(base_bare_t,5,_vovw_5_base_bare_t)
(base_t,0,_vovw_0_base_t)
(base_t,1,_vovw_1_base_t)
(base_t,2,_vovw_2_base_t)
(base_t,3,_vovw_3_base_t)
(base_t,4,_vovw_4_base_t)
(base_t,5,_vovw_5_base_t)
(column_types_t,0,_vovw_0_column_types_t)
(column_types_t,1,_vovw_1_column_types_t)
(column_types_t,2,_vovw_2_column_types_t)
(column_types_t,3,_vovw_3_column_types_t)
(column_types_t,4,_vovw_4_column_types_t)
(column_types_t,5,_vovw_5_column_types_t)
ERROR: relation "_vovw_5_base_t" does not exist
LINE 1: SELECT count(*) FROM _vovw_5_base_t;
ERROR: relation "_vovw_2_base_t" does not exist
LINE 1: SELECT count(*) FROM _vovw_2_base_t;
^
{_vovw_5_base_t,_vovw_4_base_t,_vovw_3_base_t,_vovw_2_base_t,_vovw_1_base_t,_vovw_0_base_t}
38
DROP TABLE
DROP TABLE
DROP TABLE