implement search with own custom planner

Author: e-e-e

index.js

@@ -4,7 +4,8 @@ const pump = require('pump')
 const utils = require('./lib/utils')
 const Variable = require('./lib/Variable')
 const HyperdbDiffTransform = require('./lib/HyperdbDiffTransform')
-const planner = require('./lib/queryPlanner')
+const JoinStream = require('./lib/JoinStream')
+const planner = require('./lib/planner')
 
 function Graph (db, opts) {
   if (!(this instanceof Graph)) return new Graph(db, opts)
@@ -54,8 +55,7 @@ Graph.prototype.searchStream = function (query, options) {
   const plannedQuery = planner(query)
 
   var streams = plannedQuery.map((triple) => {
-    const stream = triple.stream
-    return stream({ triple: utils.filterTriple(triple), db: this, index: triple.index })
+    return new JoinStream({ triple, db: this })
   })
 
   streams[0].start = true

lib/SortJoinStream.js

@@ -0,0 +1,63 @@
+
+const utils = require('./utils')
+
+function planner (query) {
+  if (query.length === 1) return query
+  // first group queries based on number of variables.
+  const solved = new Set()
+  var grouped = query.reduce((ordered, q) => {
+    const variables = utils.variableNames(q)
+    if (ordered[variables.length]) {
+      ordered[variables.length].push({
+        query: q,
+        names: variables
+      })
+    } else {
+      ordered[variables.length] = [{
+        query: q,
+        names: variables
+      }]
+    }
+    if (variables.length === 1) {
+      solved.add(variables[0])
+    }
+    return ordered
+  }, [])
+  // then order vars > 1 by if they occur in
+  const orderedQueries = grouped[1] ? grouped[1].map(v => v.query) : []
+
+  for (let i = 2; i < grouped.length; i++) {
+    if (grouped[i] === undefined) continue
+    while (grouped[i].length > 0) {
+      // get the next easiest to solve
+      // or the one that makes the rest easiest to solve
+      grouped[i].sort((a, b) => {
+        // number of unsolved variables
+        let unsolvedA = a.names.filter(name => !solved.has(name))
+        let unsolvedB = b.names.filter(name => !solved.has(name))
+        if (unsolvedA.length < unsolvedB.length) return -1
+        if (unsolvedA.length > unsolvedB.length) return 1
+        // calculate how many unsolved vars it has in common with others in the group
+        // should this be a vector? many vars is better than solving 1 lots.
+        let sharedUnsolvedA = 0
+        let sharedUnsolvedB = 0
+        grouped[i].forEach(v => {
+          v.names.forEach((name) => {
+            if (solved.has(name)) return
+            if (v !== a && a.names.includes(name)) sharedUnsolvedA++
+            if (v !== b && b.names.includes(name)) sharedUnsolvedB++
+          })
+        })
+        if (sharedUnsolvedA > sharedUnsolvedB) return -1
+        if (sharedUnsolvedA < sharedUnsolvedB) return 1
+        return 0
+      })
+      const next = grouped[i].shift()
+      orderedQueries.push(next.query)
+      next.names.forEach(n => solved.add(n))
+    }
+  }
+  return orderedQueries
+};
+
+module.exports = planner

lib/planner.js

@@ -139,6 +139,12 @@ function objectMask (criteria, obj) {
     }, {})
 };
 
+function variableNames (obj) {
+  return Object.keys(obj)
+    .filter(key => hasKey(key) && keyIsAVariable(obj[key]))
+    .map(key => obj[key].name)
+};
+
 function queryMask (object) {
   return objectMask(keyIsNotAObject, object)
 };
@@ -150,15 +156,14 @@ function maskUpdater (pattern) {
   const variables = variablesMask(pattern)
   return (solution, mask) => {
     const maskCopy = Object.assign({}, mask)
-    return Object.keys(variables).reduce((newMask, key) => {
-      const variable = variables[key]
-      if (variable.isBound(solution)) {
-        newMask[key] = solution[variable.name]
-      }
-      // fix this
-      newMask.filter = pattern.filter
-      return newMask
-    }, maskCopy)
+    return Object.keys(variables)
+      .reduce((newMask, key) => {
+        const variable = variables[key]
+        if (variable.isBound(solution)) {
+          newMask[key] = solution[variable.name]
+        }
+        return newMask
+      }, maskCopy)
   }
 }
 
@@ -196,6 +201,7 @@ module.exports = {
   createQuery,
   queryMask,
   variablesMask,
+  variableNames,
   maskUpdater,
   matcher,
   materializer

lib/queryPlanner.js

@@ -15,8 +15,8 @@
     "standard": "^10.0.3"
   },
   "scripts": {
-    "test": "mocha test",
-    "ttd": "mocha test -w"
+    "test": "mocha test/**.spec.js",
+    "ttd": "mocha test/**.spec.js -w"
   },
   "author": "Benjamin Forster",
   "license": "MIT"