Method getDataExtent

src/data/DataStore.ts:1135–1196

(
        dim: DimensionIndex,
        filter: DataSanitizationFilter | NullUndefined
    )

    }

    getDataExtent(
        dim: DimensionIndex,
        filter: DataSanitizationFilter | NullUndefined
    ): [number, number] {
        // Make sure use concrete dim as cache name.
        const dimData = this._chunks[dim];
        const initialExtent = initExtentForUnion();

        if (!dimData) {
            return initialExtent;
        }

        // Make more strict checkings to ensure hitting cache.
        const currEnd = this.count();

        // Consider the most cases when using data zoom, `getDataExtent`
        // happened before filtering. We cache raw extent, which is not
        // necessary to be cleared and recalculated when restore data.
        const useRaw = !this._indices && !filter;
        if (useRaw) {
            return this._rawExtent[dim].slice() as [number, number];
        }

        // NOTE:
        //  - In logarithm axis, zero should be excluded, therefore the `extent[0]` should be less or equal
        //    than the min positive data item, which requires the special handling here.
        //  - "Filter non-positive values for logarithm axis" can also be implemented in a data processor
        //    but that requires more complicated code to not break all streams under the current architecture,
        //    therefore we simply implement it here.
        //  - Performance is sensitive for large data, therefore inline filters rather than cb is used here.

        const thisExtent = this._extent;
        const dimExtentRecord = thisExtent[dim] || (thisExtent[dim] = {});

        const filterParsed = parseSanitizationFilter(filter);
        const filterKey = filterParsed.key;

        const dimExtent = dimExtentRecord[filterKey];
        if (dimExtent) {
            return dimExtent.slice() as [number, number];
        }

        let min = initialExtent[0];
        let max = initialExtent[1];

        for (let i = 0; i < currEnd; i++) {
            // NOTICE: Manually inline some code for performance of large data.
            const rawIdx = this.getRawIndex(i);
            const value = dimData[rawIdx] as ParsedValueNumeric;
            // NOTE: in most cases, filter does not exist.
            if (!filter || passesSanitizationFilter(filterParsed, value)) {
                if (value < min) {
                    min = value;
                }
                if (value > max) {
                    max = value;
                }
            }