@sqlrooms/deck / prepareDeckDataset

Function: prepareDeckDataset()

prepareDeckDataset(options): PreparedDeckDataset

Build the reusable deck-facing geometry helpers for one resolved Arrow table.

This is the expensive preparation step that preparedDatasetStore caches. It accepts one resolved Arrow table plus a geometry column/hint and turns the source geometry into canonical deck-facing outputs that can be reused by multiple layers and multiple DeckJsonMap instances.

Supported input geometry forms:

• native GeoArrow columns Already columnar and geometry-aware. These are the cheapest inputs: preparation mainly does geometry-column detection plus lightweight wrapper shaping so GeoArrow-capable deck layers can consume the Arrow table/vector directly.
• WKB / GeoArrow WKB columns Binary geometry needs decoding because deck layers cannot render raw WKB bytes. Preparation promotes the binary values into deck-ready geometry structures for GeoArrow layers and GeoJSON-binary fallback layers.
• WKT / GeoArrow WKT columns Text geometry likewise needs parsing before deck can render it. This has a similar cost profile to WKB, but starts from text parsing rather than binary decoding.

These transformations are necessary because the input table shape is chosen by the query/data source, while deck expects render-oriented geometry payloads. The canonical outputs produced here are:

• GeoArrow layer data A PreparedGeoArrowLayerData payload for GeoArrow-native deck layers, either forwarded directly from native GeoArrow inputs or promoted from WKB/WKT into a GeoArrow-like representation.
• GeoJSON-binary data A binary GeoJSON-style payload for layers such as GeoJsonLayer that do not consume GeoArrow inputs directly.

The returned object also memoizes:

• geometry column detection
• GeoArrow layer payloads
• GeoJSON-binary fallbacks

Caching at this level lets deck reuse geometry decoding and shaping work even when the upstream query result is already cached by another system such as Mosaic's query manager.

Parameters

Parameter	Type
options	PrepareDeckDatasetOptions

Returns

PreparedDeckDataset