Issue #94: Update view join algorithm

Signed-off-by: rafaelatc3sl <rpd17@c3sl>

src/util/viewHandler.ts

@@ -116,7 +116,7 @@ export class ViewHandler {
         partialJoin = views.map((i) => (i));
 
         if (q.metrics.length === 0) { // ignore metView if there are 0 metrics
-            while (partialJoin.length > 1) {
+            if (partialJoin.length > 0) {
                 qOpt = {metrics: partialQuery.metrics, dimensions: partialQuery.dimensions, clauses: clausesToCover};
                 partialQuery = new Query(qOpt);
                 reduced = ViewHandler.applyReduce(partialJoin, partialQuery);
@@ -134,7 +134,7 @@ export class ViewHandler {
 
             metView = partialJoin[metViewId];
             partialJoin.splice(metViewId, 1);
-            while (partialJoin.length > 1) {
+            if (partialJoin.length > 0) {
                 partialJoin.push(metView); // MetView is now the last view
                 qOpt = {metrics: partialQuery.metrics, dimensions: partialQuery.dimensions, clauses: clausesToCover};
                 partialQuery = new Query(qOpt);
@@ -309,76 +309,33 @@ export class ViewHandler {
     }
 
     /**
-     * Finds the pair of views most realted in a set of views and
-     * applies the JOIN operation in this set.
-     * Returns a set with the joined view and without the most
-     * related view.
+     * Apply JOIN operation in a set of views.
+     * Returns a set with the joined view. 
      * @param v - Set of candidated views to be joined.
      */
     private static applyJoin(v: View[]): View[] {
-        /*
-            At this point 2 views will be joined, first the
-            similarity with each pair of views is calculated,
-            the pair with the biggedt similarity will be joined.
         
-            Similarity is calculated with the number of common
-            dimensions in the keys.
-        */
         const views = v.map((i) => i);
-        let similarity = 0;
-        let idx0 = 0;
-        let idx1 = 1;
-        for (let i = 0; i < views.length; ++i) {
-            for (let j = i + 1 ; j < views.length; ++j) {
-                const pi = views[i].dimensions;
-                const pj = views[j].dimensions;
-                let score = this.similarDimensions (pi, pj);
-                if (similarity < score) {
-                    similarity = score;
-                    idx0 = i;
-                    idx1 = j;
-                }
-            }
-        }
 
-        const partial0 = views[idx0];
-        const partial1 = views[idx1];
+        let dims: Dimension[] = [];
+        let mets: Metric[] = [];
+        let clauses: Clause[] = [];
 
-        views.splice(idx1, 1);
-        views.splice(idx0, 1);
+        for (let i = 0; i < views.length; ++i) {
+            mets = mets.concat(views[i].metrics);
+            dims = dims.concat(views[i].dimensions);
+            clauses = clauses.concat(views[i].clauses);
+        }
 
-        let dims = partial0.dimensions.concat(partial1.dimensions);
         dims = ViewHandler.removeDuplicatedDimensions(dims);
-
-        let mets = partial0.metrics.concat(partial1.metrics);
         mets = ViewHandler.removeDuplicatedMetrics(mets);
-
-        let clauses = partial0.clauses.concat(partial1.clauses);
         clauses = ViewHandler.removeDuplicatedClauses(clauses);
 
         const qOpts: QueryOpts = {metrics: mets, dimensions: dims, clauses: clauses};
-
         const partialQuery = new Query(qOpts);        
 
-        const partial = ViewHandler.queryJoin(partialQuery, [partial0, partial1]);
-        views.push(partial);
-        return views;
-    }
-
-    /**
-     * Calculates the similarity of two sets of dimensions. In other
-     * other how many dimensions are in both sets.
-     * @param a - A set of dimensions.
-     * @param b - Another set of dimensions.
-     */
-    private static similarDimensions(a: Dimension[], b: Dimension[]): number {
-        let count = 0;
-        for (let i = 0; i < a.length; ++i) {
-            if (b.some((itemB) => a[i].name === itemB.name)) {
-                count++;
-            }
-        }
-        return count;
+        const partial = ViewHandler.queryJoin(partialQuery, views);
+        return [partial];
     }
 
     /**