From 6241b23d4f5ef9c99aa774b6ccb60a513eafb6d7 Mon Sep 17 00:00:00 2001
From: Raul Marin <git@rmr.ninja>
Date: Mon, 4 Mar 2019 14:09:30 +0100
Subject: [PATCH] Histogram: Speed up IRQ calculation

---
 .../dataview/histograms/numeric-histogram.js  | 20 ++++++-------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/lib/cartodb/models/dataview/histograms/numeric-histogram.js b/lib/cartodb/models/dataview/histograms/numeric-histogram.js
index ddf3577f..51980b84 100644
--- a/lib/cartodb/models/dataview/histograms/numeric-histogram.js
+++ b/lib/cartodb/models/dataview/histograms/numeric-histogram.js
@@ -15,24 +15,15 @@ const irqQueryTpl = ctx => `
         SELECT
             max(${ctx.column}) AS __cdb_max_val,
             min(${ctx.column}) AS __cdb_min_val,
-            count(1) AS __cdb_total_rows
+            count(1) AS __cdb_total_rows,
+            ${ctx.irq ? ctx.irq : `0`} AS __cdb_iqr
         FROM __cdb_filtered_source
     )
 `;
 
-/* Query to calculate the number of bins (needs irqQueryTpl before it*/
+/* Query to calculate the number of bins (needs irqQueryTpl before it.
+ * It uses the Freedman–Diaconis rule to calculate the witdh of the bins */
 const binsQueryTpl = ctx => `
-    __cdb_iqrange AS (
-        SELECT max(quartile_max) - min(quartile_max) AS __cdb_iqr
-        FROM (
-            SELECT quartile, max(_cdb_iqr_column) AS quartile_max from (
-                SELECT ${ctx.column} AS _cdb_iqr_column, ntile(4) over (order by ${ctx.column}
-            ) AS quartile
-            FROM __cdb_filtered_source) _cdb_quartiles
-            WHERE quartile = 1 or quartile = 3
-            GROUP BY 1
-        ) __cdb_iqr
-    ),
     __cdb_bins AS (
         SELECT
             CASE WHEN __cdb_total_rows = 0 OR __cdb_iqr = 0
@@ -45,7 +36,7 @@ const binsQueryTpl = ctx => `
                 )
             )
             END AS __cdb_bins_number
-        FROM __cdb_basics, __cdb_iqrange, __cdb_filtered_source
+        FROM __cdb_basics, __cdb_filtered_source
         LIMIT 1
     )
 `;
@@ -118,6 +109,7 @@ module.exports = class NumericHistogram extends BaseHistogram {
 
         if (ctx.bins <= 0) {
             ctx.bins = `__cdb_bins.__cdb_bins_number`;
+            ctx.irq = `percentile_disc(0.75) within group (order by ${ctx.column}) - percentile_disc(0.25) within group (order by ${ctx.column})`;
             extra_groupby += `, __cdb_bins.__cdb_bins_number`;
             extra_tables += `, __cdb_bins`;
             extra_queries = `WITH ${irqQueryTpl(ctx)}, ${binsQueryTpl(ctx)}`;