From f94aa4ec99c3ce2de0f345859b10daad85b9ef2a Mon Sep 17 00:00:00 2001
From: Paul Trowbridge <paul@hptrow.me>
Date: Fri, 18 Sep 2026 08:16:09 -0400
Subject: [PATCH] Drop the measure name from a collapsed column's slice

Clicking a bucket subtotal with the month level collapsed produced
{"customer": "...", "pf_bucket": "04 - Forecast", "smon_e": "sales_usd"} --
a month equal to a measure, matching nothing, so the ledger came back empty
and an operation would have had no rows to act on.

Perspective maps split_by positionally over the column name, and a collapsed
axis has fewer segments than there are split_by levels, so the measure lands
on the first hidden dimension. Both slice paths now drop any == filter whose
value is one of the view's measures; the region path additionally takes the
measure off the end of the column name before mapping, which is the same
error made in our own code.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
---
 ui/src/views/Forecast.jsx | 31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/ui/src/views/Forecast.jsx b/ui/src/views/Forecast.jsx
index dc8f382..5982bfd 100644
--- a/ui/src/views/Forecast.jsx
+++ b/ui/src/views/Forecast.jsx
@@ -323,13 +323,23 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
       for (let c = c0; c < c1; c++) {
         const key = userKeys[c]
         if (!key) continue
+        // A column name is dimension values joined by | with the measure last, and
+        // only as many values as the axis currently shows -- collapse the column
+        // hierarchy and the deeper levels are simply absent. Mapping split_by
+        // positionally over every segment therefore read the measure as a value
+        // for the first collapsed dimension: a bucket subtotal came back as
+        // smon_e = 'sales_usd', which matches no row, so the operation silently
+        // had nothing to act on. Drop the measure, then map over what is left.
+        const segs = key.split('|').slice(0, -1)
         const colFilters = splitBy
+          .slice(0, segs.length)
           .map((col, ix) => {
-            const v = key.split('|')[ix]
+            const v = segs[ix]
             return (v && !META_COL_RE.test(v)) ? [col, '==', v] : null
           })
           .filter(Boolean)
-        const slice = sliceFromFilters([...base, ...rowFilters, ...colFilters])
+        const slice = sliceFromFilters([...base, ...rowFilters, ...colFilters],
+                                       (cfg.columns || []).filter(Boolean))
         if (!Object.keys(slice).length) continue
         const y = win.start_row + i
         out.push({ slice, area: { x0: c, x1: c, y0: y, y1: y } })
@@ -770,7 +780,8 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
         if (!detail.row) return
         const config = await viewer.save()
         if (!(config.group_by || []).length) return
-        const s = sliceFromFilters((detail.config || {}).filter || [])
+        const s = sliceFromFilters((detail.config || {}).filter || [],
+                                   (config.columns || []).filter(Boolean))
         if (!Object.keys(s).length) return
         // the CustomEvent carries no modifier flags, so read them off the
         // mousedown that produced it (captured on window below)
@@ -1948,12 +1959,22 @@ function LogCell({ entry, field, placeholder, editing, setEditing, onSave, listI
 const META_COL_RE = /^__(?:ROW_PATH(?:_\d+)?|ID|GROUPING_ID)__$/
 
 // Perspective encodes a clicked/selected row position as [col, '==', value] triples
-function sliceFromFilters(filters) {
+// `measures` is the view's `columns` list. Clicking a cell whose column axis is
+// collapsed makes Perspective emit the measure name as the value of the first
+// hidden split_by dimension -- a bucket subtotal arrives as
+// ["smon_e", "==", "sales_usd"] -- because the engine maps split_by positionally
+// over a column name that no longer has that many segments. Left in, the slice
+// asks for a month equal to a measure, matches nothing, and the operation
+// silently has no rows to act on.
+function sliceFromFilters(filters, measures = []) {
+  const measureSet = new Set(measures)
   const s = {}
   for (const f of filters) {
     if (!Array.isArray(f)) continue
     const [col, op, val] = f
-    if (op === '==' && val != null) s[col] = String(val)
+    if (op !== '==' || val == null) continue
+    if (measureSet.has(String(val))) continue
+    s[col] = String(val)
   }
   return s
 }