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Refactor aggregation resolution

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This commit is contained in:
Javier Goizueta 2017-12-14 16:51:55 +01:00
parent e4407ece84
commit 9d8ce6bc44
1 changed files with 10 additions and 6 deletions
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16
lib/cartodb/models/aggregation/aggregation-query.js
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@ -78,9 +78,14 @@ const aggregateColumnDefs = ctx => {
}).join(', ');
};
// SQL expression to compute the aggregation resolution (grid cell size).
// This is equivalent to `${256/ctx.res}*CDB_XYZ_Resolution(CDB_ZoomFromScale(!scale_denominator!))`
// This is defined by the ctx.res parameter, which is the number of grid cells per tile linear dimension
// (i.e. each tile is divided into ctx.res*ctx.res cells).
const gridResolution = ctx => `(${256*0.00028/ctx.res}*!scale_denominator!)::double precision`;
// Notes:
// * ${256*0.00028/ctx.res}*!scale_denominator! is equivalent to
// ${256/ctx.res}*CDB_XYZ_Resolution(CDB_ZoomFromScale(!scale_denominator!))
// * We need to filter spatially using !bbox! to make the queries efficient because
// the filter added by Mapnik (wrapping the query)
// is only applied after the aggregation.
@ -90,7 +95,7 @@ const aggregationQueryTemplates = {
'centroid': ctx => `
WITH _cdb_params AS (
SELECT
(${256*0.00028/ctx.res}*!scale_denominator!)::double precision AS res,
${gridResolution(ctx)} AS res,
!bbox! AS bbox
)
SELECT
@ -112,7 +117,7 @@ const aggregationQueryTemplates = {
'point-grid': ctx => `
WITH _cdb_params AS (
SELECT
(${256*0.00028/ctx.res}*!scale_denominator!)::double precision AS res,
${gridResolution(ctx)} AS res,
!bbox! AS bbox
),
_cdb_clusters AS (
@ -133,8 +138,7 @@ const aggregationQueryTemplates = {
'point-sample': ctx => `
WITH _cdb_params AS (
SELECT
(${256*0.00028/ctx.res}*!scale_denominator!)::double precision AS res,
${gridResolution(ctx)} AS res,
!bbox! AS bbox
), _cdb_clusters AS (
SELECT