Drill-through

Every grid cell is an aggregate; drill-through answers “which rows made this number?” Given a group-key path, the engine returns the underlying source rows that rolled up into that node — the exact records behind the subtotal, optionally column-projected and row-limited. It’s the same Polars filter the aggregation used, so the answer is always consistent with the displayed value.

Dash (Python)

from dash import Input, Output, callback
from dash_tensor_grid import TensorGrid
from dash_tensor_grid.engine import GridDataEngine

engine = GridDataEngine(sales)
ROWS = ["region", "country"]

# Fire `cell_clicked` (enable_cell_click) and read its decoded group-key `path`.
grid = TensorGrid(id="grid", enable_cell_click=True, row_data=..., column_defs=...)

@callback(Output("detail", "children"), Input("grid", "cell_clicked"), prevent_initial_call=True)
def show_source(cell):
    path = cell["path"]                      # e.g. ["EMEA", "Germany"]
    rows = engine.drill_through(ROWS, path, limit=100)
    return f"{len(rows)} source rows: {rows}"

React

import { TensorGrid } from '@tensorgrid/react';
import { drillThrough } from '@tensorgrid/core';

// `masterDetail` reveals the source rows inline (it calls drillThrough under the hood):
<TensorGrid data={data} rows={['region', 'country']} measures={{ revenue: 'sum' }} masterDetail />;

// …or call the pure helper headlessly for your own panel/export:
const rows = drillThrough(data, ['region', 'country'], ['EMEA', 'Germany'], { limit: 100 });

Vue

<TensorGrid
  :data="data"
  :rows="['region', 'country']"
  :measures="{ revenue: 'sum' }"
  master-detail
/>

Vanilla JS

import { mountTensorGrid } from '@tensorgrid/vanilla';
import { drillThrough } from '@tensorgrid/core';

mountTensorGrid(document.getElementById('grid'), {
  data,
  rows: ['region', 'country'],
  measures: { revenue: 'sum' },
  masterDetail: true,
});

// Headless retrieval of the rows behind a node:
const rows = drillThrough(data, ['region', 'country'], ['EMEA', 'Germany'], { limit: 100 });

Notes

• Path-addressed. Drill-through takes the group-key path (["EMEA", "Germany"]) — exactly the path the Dash cell_clicked event decodes, so you hand it straight to engine.drill_through.
• limit and column projection. Cap the returned rows and select which source columns to bring back; the result is JSON-safe (NaN/Inf/None normalised).
• Same rows, two surfaces. Master / detail renders the drilled rows inline; selection copies/exports the drilled rows behind the selected nodes.