Add imodel_geom_stream virtual table for GeometryStream decomposition

common/api/core-backend.api.md

@@ -4283,6 +4283,8 @@ export class IModelHost {
     static get isValid(): boolean;
     static get logTileLoadTimeThreshold(): number;
     static get logTileSizeThreshold(): number;
+    // @beta
+    static get maxGeomStreamVTabBytes(): number;
     static readonly onAfterStartup: BeEvent<() => void>;
     static readonly onBeforeShutdown: BeEvent<() => void>;
     static readonly onWorkspaceStartup: BeEvent<() => void>;
@@ -4336,6 +4338,8 @@ export class IModelHostConfiguration implements IModelHostOptions {
     static defaultLogTileLoadTimeThreshold: number;
     // (undocumented)
     static defaultLogTileSizeThreshold: number;
+    // @beta
+    static defaultMaxGeomStreamVTabBytes: number;
     // @internal (undocumented)
     static defaultMaxTileCacheDbSize: number;
     // (undocumented)
@@ -4391,6 +4395,8 @@ export interface IModelHostOptions {
     // @internal
     logTileSizeThreshold?: number;
     // @beta
+    maxGeomStreamVTabBytes?: number;
+    // @beta
     maxTileCacheDbSize?: number;
     // @beta
     profileName?: string;

common/changes/@itwin/core-backend/affan.khan-geom-stream-vtab-and-scalar-fns_2026-04-24-22-00.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@itwin/core-backend",
+      "comment": "Add imodel_geom_stream virtual table for GeometryStream decomposition",
+      "type": "none"
+    }
+  ],
+  "packageName": "@itwin/core-backend"
+}

core/backend/src/IModelHost.ts

@@ -155,6 +155,13 @@ export interface IModelHostOptions {
    */
   maxTileCacheDbSize?: number;
 
+  /** The process-wide maximum uncompressed GeometryStream size in bytes that the `dgn_geom_stream` virtual table will decompose.
+   * Blobs exceeding this limit are silently skipped (the vtab returns zero rows for them).
+   * Defaults to 50 MB. Minimum enforced by native layer: 4 KB.
+   * @beta
+   */
+  maxGeomStreamVTabBytes?: number;
+
   /** Whether to restrict tile cache URLs by client IP address (if available).
    * @beta
    */
@@ -249,6 +256,10 @@ export class IModelHostConfiguration implements IModelHostOptions {
   public static defaultLogTileSizeThreshold = 20 * 1000000;
   /** @internal */
   public static defaultMaxTileCacheDbSize = 1024 * 1024 * 1024;
+  /** Default maximum uncompressed GeometryStream size (50 MB) for the `imodel_geom_stream` virtual table.
+   * @beta
+   */
+  public static defaultMaxGeomStreamVTabBytes = 50 * 1024 * 1024;
   public appAssetsDir?: LocalDirName;
   public cacheDir?: LocalDirName;
 
@@ -669,6 +680,7 @@ export class IModelHost {
 
     this.configuration = otherOptions;
     this.setupTileCache();
+    IModelNative.platform.setMaxGeomStreamVTabBytes(otherOptions.maxGeomStreamVTabBytes ?? IModelHostConfiguration.defaultMaxGeomStreamVTabBytes);
 
     process.once("beforeExit", IModelHost.shutdown);
     this.onAfterStartup.raiseEvent();
@@ -798,6 +810,16 @@ export class IModelHost {
     return undefined !== IModelHost.configuration && (IModelHost.configuration.useSemanticRebase ? true : false);
   }
 
+  /**
+   * The current process-wide maximum uncompressed GeometryStream size in bytes that the `dgn_geom_stream`
+   * virtual table will decompose. Blobs exceeding this limit are silently skipped.
+   * @see [[IModelHostOptions.maxGeomStreamVTabBytes]]
+   * @beta
+   */
+  public static get maxGeomStreamVTabBytes(): number {
+    return IModelNative.platform.getMaxGeomStreamVTabBytes();
+  }
+
   private static setupTileCache() {
     assert(undefined !== IModelHost.configuration);
     const config = IModelHost.configuration;