diff --git a/lib/sql_generator.js b/lib/sql_generator.js
index 3d655b9..62bd0b3 100644
--- a/lib/sql_generator.js
+++ b/lib/sql_generator.js
@@ -224,6 +224,22 @@ function generateSQL(source, colMeta) {
     const cloneCols = [...dims, ...dateCols, effectiveValue, effectiveUnits].filter(Boolean);
     const cloneInsertCols = [...cloneCols.map(q), 'pf_iter', 'pf_logid', 'pf_user', 'pf_created_at'].join(', ');
 
+    // An adjustment writes one row per *coordinate* it touches, not one per row
+    // it reads.
+    //
+    // Reading rows one-for-one meant every operation inherited the row count of
+    // everything before it: the baseline's rows plus every prior adjustment's
+    // rows at the same coordinate, so the table grew super-linearly with how
+    // much work had been done on it. Eight Pull Forward entries and the next
+    // scale over the same slice writes nine times what it needs to.
+    //
+    // Collapsing is over pf_logid and pf_iter only -- every stored dimension and
+    // date stays in the GROUP BY -- so no column goes null and nothing becomes
+    // unsliceable later. The distribution maths is untouched either way, since
+    // the window sums see the same totals whether or not the rows underneath
+    // them have been added up first.
+    const groupCols       = (cols) => cols.map(q).join(',\n        ');
+
     const loadCols        = [...dims, ...dateCols, ...valueCols, ...unitsCols];
     const loadInsertCols  = [...loadCols.map(q), 'pf_iter', 'pf_logid', 'pf_user', 'pf_created_at'].join(', ');
     const dateColSet      = new Set(dateCols);
@@ -388,13 +404,16 @@ SELECT count(*) AS rows_affected FROM ins`.trim();
         const uSel = effectiveUnits
             ? `round((${q(effectiveUnits)} / NULLIF(total_units, 0)) * {{units_incr}}, 5)`
             : `0`;
+        // sum(sum(x)) OVER () is the aggregate of the aggregates: the window runs
+        // after the GROUP BY, so the total is over collapsed coordinates and
+        // comes to the same figure the ungrouped window produced.
         const baseSelectParts = [
             ...dimsJoined ? [dimsJoined] : [],
             q(dateCol),
-            effectiveValue  ? q(effectiveValue)  : null,
-            effectiveUnits  ? q(effectiveUnits)  : null,
-            effectiveValue  ? `sum(${q(effectiveValue)}) OVER () AS total_value`  : null,
-            effectiveUnits  ? `sum(${q(effectiveUnits)}) OVER () AS total_units` : null
+            effectiveValue  ? `sum(${q(effectiveValue)}) AS ${q(effectiveValue)}` : null,
+            effectiveUnits  ? `sum(${q(effectiveUnits)}) AS ${q(effectiveUnits)}` : null,
+            effectiveValue  ? `sum(sum(${q(effectiveValue)})) OVER () AS total_value` : null,
+            effectiveUnits  ? `sum(sum(${q(effectiveUnits)})) OVER () AS total_units` : null
         ].filter(Boolean).join(',\n        ');
         return `
 WITH
@@ -409,6 +428,8 @@ ilog AS (
     FROM {{fc_table}}
     WHERE {{where_clause}}
     {{exclude_clause}}
+    GROUP BY
+        ${groupCols([...dims, dateCol])}
 )
 ,ins AS (
     INSERT INTO {{fc_table}} (${insertCols})
@@ -430,10 +451,14 @@ ilog AS (
     RETURNING id
 )
 ,src AS (
-    SELECT ${selectData}
+    SELECT
+        ${dimsJoined},
+        ${q(dateCol)}${effectiveValue ? `,\n        sum(${q(effectiveValue)}) AS ${q(effectiveValue)}` : ''}${effectiveUnits ? `,\n        sum(${q(effectiveUnits)}) AS ${q(effectiveUnits)}` : ''}
     FROM {{fc_table}}
     WHERE {{where_clause}}
     {{exclude_clause}}
+    GROUP BY
+        ${groupCols([...dims, dateCol])}
 )
 ,neg AS (
     INSERT INTO {{fc_table}} (${insertCols})
@@ -480,9 +505,15 @@ ilog AS (
     SELECT
         ${select},
         'clone', (SELECT id FROM ilog), '{{pf_user}}', now()
-    FROM {{fc_table}} s${hasDimPeriod ? dimPeriodJoins(dateGroups) : ''}
-    WHERE {{where_clause}}
-    {{exclude_clause}}
+    FROM (
+        SELECT
+            ${groupCols([...dims, ...dateCols])}${effectiveValue ? `,\n            sum(${q(effectiveValue)}) AS ${q(effectiveValue)}` : ''}${effectiveUnits ? `,\n            sum(${q(effectiveUnits)}) AS ${q(effectiveUnits)}` : ''}
+        FROM {{fc_table}}
+        WHERE {{where_clause}}
+        {{exclude_clause}}
+        GROUP BY
+            ${groupCols([...dims, ...dateCols])}
+    ) s${hasDimPeriod ? dimPeriodJoins(dateGroups) : ''}
     RETURNING *
 )
 ${opTail('ins')}`.trim();