Expression Query

When CAD drawings are opened directly in memory mode, there is no process of converting to a spatial database, so the frontend cannot perform custom queries on backend data via sql. Queries can only be performed through js scripts or through expressions. For expression syntax details, see the document Server-side Rendering Expression Syntax.

Tip

js scripts are easier to understand and get started with, but slightly slower in performance Expressions are harder to understand and master, but perform better We recommend using js scripts

Built-in Variables

Variable	Description	Type	Example
gInLayerIndex	Current entity layer index	(numeric)	0
gInObjectId	Current entity object ID	(string)	'283' e.g. gInObjectId=='283'
gInFeatureType	Current entity type	(string)	'AcDbPolyline' e.g. gInFeatureType=='AcDbPolyline'
gInLayerName	Current entity layer name	(string)	'Layer1' e.g. gInLayerName=='Layer1'
gInColor	Current entity color	(numeric)	4278255615
gInColorRed	Current entity color (red component)	(numeric)	255
gInColorGreen	Current entity color (green component)	(numeric)	255
gInColorBlue	Current entity color (blue component)	(numeric)	0
gInColorAlpha	Current entity color (alpha component)	(numeric)	0
println	Debug output function
gInExtendMinX	Current entity extent (bottom-right X)	(numeric)	700.10
gInExtendMinY	Current entity extent (bottom-right Y)	(numeric)	10.01
gInExtendMaxX	Current entity extent (top-left X)	(numeric)	800.20
gInExtendMaxY	Current entity extent (top-left Y)	(numeric)	20.02
gInAttrs1	Current entity attribute 1 value	(string) s1 linetype
gInAttrs2	Current entity attribute 2 value	(string) s2 extended dictionary data
gInAttrs3	Current entity attribute 3 value	(string) s3 varies by entity type
gInAttrs4	Current entity attribute 4 value	(string) s4 string attribute data, varies by entity type
gInAttrs5	Current entity attribute 5 value	(string) s5 string attribute data, varies by entity type
gInAttrn6	Current entity attribute 6 value	(numeric) n1 color index
gInAttrn7	Current entity attribute 7 value	(numeric) n2 linetype scale
gInAttrn8	Current entity attribute 8 value	(numeric) n3 line width
gInAttrn9	Current entity attribute 9 value	(numeric) n4 transparency
gInAttrn10	Current entity attribute 10 value	(numeric) n5 numeric attribute data, varies by entity type
gInAttrn11	Current entity attribute 11 value	(numeric) n6 varies by entity type
gInAttrn12	Current entity attribute 12 value	(numeric) n7 varies by entity type
gInAttrn13	Current entity attribute 13 value	(numeric) n8 varies by entity type
gInAttrn14	Current entity attribute 14 value	(numeric) n9 varies by entity type
gInAttrn15	Current entity attribute 15 value	(numeric) n10 varies by entity type
gInCoordX	Current entity X coordinate array	(numeric array)	[10,20...] gInCoordX[0]=10
gInCoordY	Current entity Y coordinate array	(numeric array)	[10,20...] gInCoordY[0]=10
gInCoordZ	Current entity Z coordinate array	(numeric array)	[10,20...] gInCoordZ[0]=10
gInCoordCount	Current entity coordinate count	(numeric)	2
gOutColorRed	Output color (red component) (modify current entity color)	(numeric)	255, e.g. gOutColorRed := 255; means all levels have red component 255; can also be array, e.g. gOutColorRed[0] := 122;gOutColorRed[5] := 200; means levels 1-4 have red 122, level 5+ has red 200
gOutColorGreen	Output color (green component) (modify current entity color)	(numeric)	255, same usage as above
gOutColorBlue	Output color (blue component) (modify current entity color)	(numeric)	255, same usage as above
gOutColorAlpha	Output color (alpha component) (modify current entity color)	(numeric)	255, same usage as above
gOutLineWidth	Output line width (modify current entity line width)	(numeric)	3, same usage as above
gOutVisible	Output visibility (modify current entity visibility)	(numeric)	1 or 0, same usage as above
gOutReturn	0 do not add to selection set; 1 add to selection set

Supported CAD Entity Types

Class Name	Description	Type Value
AcDbLine	Line	1
AcDbPolyline	Polyline	2
AcDb2dPolyline	2D Polyline	3
AcDb3dPolyline	3D Polyline	4
AcDbSpline	Spline	5
AcDbArc	Arc	6
AcDbCircle	Circle	7
AcDbEllipse	Ellipse	8
AcDbCurve	Curve	9
AcDbBlockReference	Block Reference	10
AcDbHatch	Hatch	11
AcDbMText	Multiline Text	12
AcDbText	Single-line Text	13
AcDbShape	Shape	14
AcDbRasterImage	Raster Image	15
AcDbWipeout	Wipeout	16
AcDb2LineAngularDimension	Angular Dimension [two lines]	17
AcDb3PointAngularDimension	Angular Dimension [three points]	18
AcDbAlignedDimension	Aligned Dimension	19
AcDbArcDimension	Arc Dimension	20
AcDbDiametricDimension	Diametric Dimension	21
AcDbOrdinateDimension	Ordinate Dimension	22
AcDbRadialDimension	Radial Dimension	23
AcDbRadialDimensionLarge	Radial Dimension Large	24
AcDbRotatedDimension	Rotated Dimension	25
AcDbAttributeDefinition	Attribute Definition	26
AcDbAttribute	Block Attribute	27
AcDbTable	Table	28
AcDbMLeader	MLeader	29
AcDbRegion	Region	30
AcDbPolyFaceMesh	Polyface Mesh	31
AcDbPolygonMesh	Polygon Mesh	32
AcDbSurface	Surface	33
AcDb3dSolid	3D Solid	34
AcDbFace	3D Face	35
AcDbSolid	Solid	36

Expression Examples

Query all lines in the drawing js

return gInFeatureType=='AcDbLine'

Query all 3D polylines with layer name "Layer1" in the drawing

return (gInFeatureType=='AcDb3dPolyline' && gInLayerName=='Layer1')

Query red single-line text in the drawing

return (gInFeatureType=='AcDbText' && gInColorRed==255 &&  gInColorGreen==0 &&  gInColorBlue==0)

Query entity with objectid of 9BE in the drawing

return gInObjectId=='9BE'

Query all text in the drawing (single-line text, multiline text, attribute definition, block attribute)

return (gInFeatureType=='AcDbText' || gInFeatureType=='AcDbMText' || gInFeatureType=='AcDbAttributeDefinition' || gInFeatureType=='AcDbAttribute')

Query all block entities in the drawing

return gInFeatureType=='AcDbBlockReference'

Query lines with length 10 in the drawing

return (gInFeatureType=='AcDbLine' && gInAttrn11 == 10)

Query circles with radius 5 in the drawing

return (gInFeatureType=='AcDbCircle' && gInAttrn12 == 5)

Query all polylines in the drawing with layer "grid lines" and coordinate x greater than 10

return (gInFeatureType == 'AcDbPolyline' &&  gInLayerName == 'grid lines' && gInExtendMinX >= 10)

Query Method

 /**
 * Expression query for entities
 * @param param Parameters
 * @param cb Callback for processing each point in the result. If null is returned, the default handler is used
 */
exprQueryFeature(param: IExprQueryFeatures, cb?: (point: [number, number]) => [number, number] | null | undefined): Promise<any>;
   /**
 * Expression query entity parameters
 */
export  interface IExprQueryFeatures extends IQueryBaseFeatures {
    /** Expression. */
    expr: string;
    /** Record start position. */
    beginpos?: number;
}

When writing expressions, you need to return based on condition evaluation. Format:

return true; // or return false;

For example, to query all block entities in the drawing, the expression is:

return gInFeatureType == 'AcDbBlockReference'

Query usage:

let query = await svc.exprQueryFeature({
    // Expression syntax
    // expr: `gOutReturn := if((gInFeatureType == 'AcDbPolyline' and  gInLayerName == 'grid lines' and gInExtendMinX >= ${center.x} ), 1, 0);`,
    // Now also supports js syntax
    // expr: `if (gInFeatureType == 'AcDbPolyline' &&  gInLayerName == 'grid lines' && gInExtendMinX >= ${center.x} ) {
    //         return true;
    //     } else {
    //         return false;
    //     }`,
    // Filter all block entities (expression syntax)
    // expr: `gOutReturn := if((gInFeatureType == 'AcDbBlockReference'), 1, 0);`,
    // Filter all block entities (js syntax)
    expr: `return gInFeatureType == 'AcDbBlockReference'`,
    fields: "objectid,blockname,envelop",
    useCache: true,
    limit: 1000000 // Large value, equivalent to finding all
})

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Combining Expression Query and SQL Query

View online demo: Multiple queries for maximum sub-entity area of block objects (opens new window)

// --Multiple queries for maximum sub-entity area of block objects--Query the entity with the largest area in blocks, first via expression query, then via condition query. Analyze results together
let svc = new vjmap.Service(env.serviceUrl, env.accessToken)
let res = await svc.openMap({
    mapid: env.exampleMapId,
    mapopenway: vjmap.MapOpenWay.GeomRender, // Open in geometry rendering mode
    style: vjmap.openMapDarkStyle()
})
if (res.error) {
    message.error(res.error)
}
let mapExtent = vjmap.GeoBounds.fromString(res.bounds);
let prj = new vjmap.GeoProjection(mapExtent);
let center = mapExtent.center();
let map = new vjmap.Map({
    container: 'map', // container ID
    style: svc.rasterStyle(),
    center: prj.toLngLat(center),
    zoom: 2,
    renderWorldCopies: false
});
map.attach(svc, prj);
map.fitMapBounds();

map.addControl(new vjmap.NavigationControl());
map.addControl(new vjmap.MousePositionControl({showZoom: true}));

// let blockNames = ["M_F13", "_AXISO"]; // Block name list to find. Block names can be found in the cloud management platform by clicking a block entity and checking blockname in the right-side properties

const handleQuery= async () => {
    let query = await svc.exprQueryFeature({
        expr: `return gInFeatureType == 'AcDbBlockReference'`,
        fields: "objectid,blockname,layername,positon,rotate,scaleX,scaleY,scaleZ", // Empty means all fields
        geom: false, // Memory mode
        useCache: true,
        limit: 1000000 // Large value, equivalent to finding all
    })
    if (query.error) {
        message.error(query.error)
        return
    }
    // Filter results by block name
    //  let findBlockName = new Set(blockNames);
    let objectIds = new Set(); // Block object objectid values
    let blockEntities = [];
    for(let i = 0; i < query.result.length; i++) {
        let blockname = query.result[i].blockname;
        // if (!findBlockName.has(blockname)) {
        // If not in the target list
        //     continue
        // }
        blockEntities.push(query.result[i])
        objectIds.add(query.result[i].objectid)
    }

    // Below, condition query for specific sub-entities contained in all blocks by objectid. This data cannot be obtained via memory query. Only after geometry processing decomposes blocks into individual sub-entities can condition query be used
    // In condition query, sub-entities of the same block all have objectid prefixed with that block's objectid_
    // Entity id
    // Block objectid naming rule: block_id_referenced_block_def_id1_referenced_block_def_id2(may have multiple)_entity_id_#;
    // Table naming rule: objectid naming rule: block_id_referenced_block_def_id1_referenced_block_def_id2(may have multiple)_entity_id_@;
    // Group objectid naming rule: $entity_id_element_index_in_entity$group_id;

    // Build sql condition, query all block objectid_ prefixed at once for efficiency
    // For fuzzy search, % can be used as wildcard in like. % defines wildcards before/after the pattern. like 'k%' finds strings ending with 'k'
    let condtionIds = Array.from(objectIds).map(id => `objectid like '${id}_%' `).join(" or ") // Concatenate all matching ids

    let condQuery = await svc.conditionQueryFeature({
        condition:  condtionIds, // objectid matching the above condition
        fields: "objectid,area",
        geom: true,
        limit: 100000 // Set large, equivalent to getting all. Default 100 if not specified
    })

    if (query.error) {
        message.error(query.error)
        return
    }
    let blockFeatures = []
    for(let i = 0; i < condQuery.result.length; i++) {
        let item = condQuery.result[i];
        blockFeatures.push(item)
    }

    // Find related entities under all blocks, find the sub-entity with maximum area
    let showDatas = []
    for(let block of blockEntities) {
        // All starting with block objectid_ are sub-entities of that block
        let blockFeature = blockFeatures.filter(b => b.objectid.indexOf(block.objectid + "_") === 0)
        let maxArea = Math.max(...blockFeature.filter(b => b.area).map(d => d.area))
        showDatas.push({
            ...block,
            area: maxArea
        })
    }
    console.table(showDatas)
    message.info(`Query result count: ${blockEntities.length} Press F12 to view console for details`);
};

handleQuery();