diff --git a/raddb/mods-config/sql/main/sqlite/process-radacct-refresh.sh b/raddb/mods-config/sql/main/sqlite/process-radacct-refresh.sh
new file mode 100755
index 000000000000..e3df0fe5d62c
--- /dev/null
+++ b/raddb/mods-config/sql/main/sqlite/process-radacct-refresh.sh
@@ -0,0 +1,112 @@
+#!/bin/sh
+#
+#  main/sqlite/process-radacct-refresh.sh -- Schema extensions and script for processing radacct entries
+#
+#  $Id$
+
+#
+#  See process-radacct-schema.sql for details.
+#
+
+if [ "$#" -ne 1 ]; then
+    echo "Usage: process-radacct-refresh.sh SQLITE_DB_FILE" 2>&1
+    exit 1
+fi
+
+if [ ! -r "$1" ]; then
+    echo "The SQLite database must exist: $1" 1>&2
+    exit 1
+fi
+
+cat <<EOF | sqlite3 "$1"
+
+    --
+    -- SQLite doesn't have a concept of session variables so we fake it.
+    --
+    DROP TABLE IF EXISTS vars;
+    CREATE TEMPORARY TABLE vars (
+        key text,
+        value text,
+        PRIMARY KEY (key)
+    );
+
+    INSERT INTO vars SELECT 'v_start', COALESCE(MAX(period_start), DATETIME(0, 'unixepoch')) FROM data_usage_by_period;
+    INSERT INTO vars SELECT 'v_end', CURRENT_TIMESTAMP;
+
+
+    --
+    -- Make of copy of the sessions that were active during this period to
+    -- avoid having to execute a potentially long transaction that might hold a
+    -- global database lock.
+    --
+    DROP TABLE IF EXISTS radacct_sessions;
+    CREATE TEMPORARY TABLE radacct_sessions (
+        username text,
+        acctstarttime datetime,
+        acctstoptime datetime,
+        acctinputoctets bigint,
+        acctoutputoctets bigint
+    );
+    CREATE INDEX temp.idx_radacct_sessions_username ON radacct_sessions(username);
+    CREATE INDEX temp.idx_radacct_sessions_acctstoptime ON radacct_sessions(acctstoptime);
+
+    INSERT INTO radacct_sessions
+        SELECT
+            username,
+            acctstarttime,
+            acctstoptime,
+            acctinputoctets,
+            acctoutputoctets
+        FROM
+            radacct
+        WHERE
+            acctstoptime > (SELECT value FROM vars WHERE key='v_start') OR
+            acctstoptime IS NULL;
+
+
+    --
+    -- Add the data usage for the sessions that were active in the current
+    -- period to the table. Include all sessions that finished since the start
+    -- of this period as well as those still ongoing.
+    --
+    INSERT INTO data_usage_by_period (username, period_start, period_end, acctinputoctets, acctoutputoctets)
+    SELECT
+        username,
+        (SELECT value FROM vars WHERE key='v_start'),
+        (SELECT value FROM vars WHERE key='v_end'),
+        SUM(acctinputoctets) AS acctinputoctets,
+        SUM(acctoutputoctets) AS acctoutputoctets
+    FROM
+        radacct_sessions
+    GROUP BY
+        username
+    ON CONFLICT(username,period_start) DO UPDATE
+        SET
+            acctinputoctets = data_usage_by_period.acctinputoctets + EXCLUDED.acctinputoctets,
+            acctoutputoctets = data_usage_by_period.acctoutputoctets + EXCLUDED.acctoutputoctets,
+            period_end = (SELECT value FROM vars WHERE key='v_end');
+
+    --
+    -- Create an open-ended "next period" for all ongoing sessions and carry a
+    -- negative value of their data usage to avoid double-accounting when we
+    -- process the next period. Their current data usage has already been
+    -- allocated to the current and possibly previous periods.
+    --
+    INSERT INTO data_usage_by_period (username, period_start, period_end, acctinputoctets, acctoutputoctets)
+    SELECT
+        username,
+        (SELECT DATETIME(value, '+1 seconds') FROM vars WHERE key='v_end'),
+        NULL,
+        0 - SUM(acctinputoctets),
+        0 - SUM(acctoutputoctets)
+    FROM
+        radacct_sessions
+    WHERE
+        acctstoptime IS NULL
+    GROUP BY
+        username;
+
+    DROP TABLE vars;
+    DROP TABLE radacct_sessions;
+
+EOF
diff --git a/raddb/mods-config/sql/main/sqlite/process-radacct-schema.sql b/raddb/mods-config/sql/main/sqlite/process-radacct-schema.sql
new file mode 100644
index 000000000000..334bd7fb6c8e
--- /dev/null
+++ b/raddb/mods-config/sql/main/sqlite/process-radacct-schema.sql
@@ -0,0 +1,51 @@
+#  -*- text -*-
+#
+#  main/sqlite/process-radacct.sql -- Schema extensions and script for processing radacct entries
+#
+#  $Id$
+
+--  ---------------------------------
+--  - Per-user data usage over time -
+--  ---------------------------------
+--
+--  An extension to the standard schema to hold per-user data usage statistics
+--  for arbitrary periods.
+--
+--  The data_usage_by_period table is populated by periodically calling the
+--  process-radacct-refresh.sh script.
+--
+--  This table can be queried in various ways to produce reports of aggregate
+--  data use over time. For example, if the refresh script is invoked once per
+--  day just after midnight, to produce usage data with daily granularity, then
+--  a reasonably accurate monthly bandwidth summary for a given user could be
+--  obtained by queriing this table with:
+--
+--      SELECT
+--          STRFTIME('%Y-%m',CURRENT_TIMESTAMP) AS month,
+--          SUM(acctinputoctets)*1.0/1000/1000/1000 AS gb_in,
+--          SUM(acctoutputoctets)*1.0/1000/1000/1000 AS gb_out
+--      FROM
+--          data_usage_by_period
+--      WHERE
+--          username='bob' AND
+--          period_end IS NOT NULL
+--      GROUP BY
+--          month;
+--
+--       2019-07|5.782279231|50.545664824
+--       2019-08|4.230543344|48.523096424
+--       2019-09|4.847360599|48.631835488
+--       2019-10|6.456763254|51.686231937
+--       2019-11|6.362537735|52.385710572
+--       2019-12|4.301524442|50.762240277
+--       2020-01|5.436280545|49.067775286
+--
+CREATE TABLE data_usage_by_period (
+    username text,
+    period_start datetime,
+    period_end datetime,
+    acctinputoctets bigint,
+    acctoutputoctets bigint,
+    PRIMARY KEY (username, period_start)
+);
+CREATE INDEX idx_data_usage_by_period_period_start ON data_usage_by_period(period_start);