beginnings of $explain

6 files changed, 192 insertions, 43 deletions

diff --git a/db/db.vcproj b/db/db.vcproj
index 54beb565bfc..db9c0254493 100644
--- a/db/db.vcproj
+++ b/db/db.vcproj
@@ -234,10 +234,6 @@
 				>

 			</File>

 			<File

-				RelativePath="..\grid\message.cpp"

-				>

-			</File>

-			<File

 				RelativePath=".\namespace.cpp"

 				>

 			</File>

@@ -250,6 +246,10 @@
 				>

 			</File>

 			<File

+				RelativePath=".\queryoptimizer.cpp"

+				>

+			</File>

+			<File

 				RelativePath=".\repl.cpp"

 				>

 			</File>

@@ -285,6 +285,10 @@
 					>

 				</File>

 				<File

+					RelativePath="..\grid\message.cpp"

+					>

+				</File>

+				<File

 					RelativePath="..\util\mmap.cpp"

 					>

 				</File>

@@ -396,6 +400,10 @@
 				>

 			</File>

 			<File

+				RelativePath=".\queryoptimizer.h"

+				>

+			</File>

+			<File

 				RelativePath=".\repl.h"

 				>

 			</File>

diff --git a/db/pdfile.h b/db/pdfile.h
index 31d134f1ae5..7bd4e5a5bed 100644
--- a/db/pdfile.h
+++ b/db/pdfile.h
@@ -309,6 +309,8 @@ inline BtreeBucket* DiskLoc::btree() const {
 
 // A Client is a psuedonym for a database. 
 
+#include "queryoptimizer.h"
+
 class Client { 
 public:
 	Client(const char *nm, bool& justCreated) : name(nm) { 
@@ -362,6 +364,7 @@ public:
 	NamespaceIndex namespaceIndex;
 	int profile; // 0=off.
 	string profileName; // "alleyinsider.system.profile"
+    QueryOptimizer optimizer;
 };
 
 // tempish...move to TLS or pass all the way down as a parm
diff --git a/db/query.cpp b/db/query.cpp
index 67a5fb98b6a..0d5d393330b 100644
--- a/db/query.cpp
+++ b/db/query.cpp
@@ -537,7 +537,8 @@ int runCount(const char *ns, BSONObj& cmd, string& err) {
 	return count;
 }
 
-/* [ { a : 1 } , { b : 1 } ] -> { a : 1, b : 1 } 
+/* This is for languages whose "objects" are not well ordered (JSON is well ordered).
+   [ { a : ... } , { b : ... } ] -> { a : ..., b : ... } 
 */
 inline BSONObj transformOrderFromArrayFormat(BSONObj order) { 
     /* note: this is slow, but that is ok as order will have very few pieces */
@@ -586,7 +587,16 @@ QueryResult* runQuery(Message& message, const char *ns, int ntoskip, int _ntoret
 
         uassert("not master", isMaster() || (queryOptions & Option_SlaveOk));
 
-		BSONObj query = jsobj.getObjectField("query");
+        bool explain = false;
+        bool _gotquery = false;
+		BSONObj query;// = jsobj.getObjectField("query");
+        {
+            BSONElement e = jsobj.findElement("query");
+            if( !e.eoo() && (e.type() == Object || e.type() == Array) ) {
+                query = e.embeddedObject();
+                _gotquery = true;
+            }
+        }
         BSONObj order;
         {
             BSONElement e = jsobj.findElement("orderby");
@@ -596,8 +606,11 @@ QueryResult* runQuery(Message& message, const char *ns, int ntoskip, int _ntoret
                     order = transformOrderFromArrayFormat(order);
             }
         }
-		if( query.isEmpty() && order.isEmpty() )
+		if( !_gotquery && order.isEmpty() )
 			query = jsobj;
+        else {
+            explain = jsobj.getBoolField("$explain");
+        }
 
 		/* The ElemIter will not be happy if this isn't really an object. So throw exception
 		   here when that is true.
@@ -607,7 +620,7 @@ QueryResult* runQuery(Message& message, const char *ns, int ntoskip, int _ntoret
 			cout << "Bad query object?\n  jsobj:";
 			cout << jsobj.toString() << "\n  query:";
 			cout << query.toString() << endl;
-			assert(false);
+            uassert("bad query object", false);
 		}
 
 		auto_ptr<JSMatcher> matcher(new JSMatcher(query));
@@ -635,8 +648,8 @@ QueryResult* runQuery(Message& message, const char *ns, int ntoskip, int _ntoret
 
 		while( c->ok() ) {
 			BSONObj js = c->current();
-			if( queryTraceLevel >= 50 )
-				cout << " checking against:\n " << js.toString() << endl;
+			//if( queryTraceLevel >= 50 )
+			//	cout << " checking against:\n " << js.toString() << endl;
 			nscanned++;
 			bool deep;
 
@@ -654,38 +667,43 @@ QueryResult* runQuery(Message& message, const char *ns, int ntoskip, int _ntoret
                 else if( ntoskip > 0 ) {
                     ntoskip--;
                 } else { 
-                    bool ok = fillQueryResultFromObj(b, filter.get(), js);
-                    if( ok ) n++;
-                    if( ok ) {
-                        if( (ntoreturn>0 && (n >= ntoreturn || b.len() > MaxBytesToReturnToClientAtOnce)) ||
-                            (ntoreturn==0 && (b.len()>1*1024*1024 || n>=101)) ) {
-                                /* if ntoreturn is zero, we return up to 101 objects.  on the subsequent getmore, there 
-                                is only a size limit.  The idea is that on a find() where one doesn't use much results, 
-                                we don't return much, but once getmore kicks in, we start pushing significant quantities.
-
-                                The n limit (vs. size) is important when someone fetches only one small field from big 
-                                objects, which causes massive scanning server-side.
-                                */
-                                /* if only 1 requested, no cursor saved for efficiency...we assume it is findOne() */
-                                if( wantMore && ntoreturn != 1 ) {
-                                    if( useCursors ) {
-                                        c->advance();
-                                        if( c->ok() ) {
-                                            // more...so save a cursor
-                                            ClientCursor *cc = new ClientCursor();
-                                            cc->c = c;
-                                            cursorid = cc->cursorid;
-                                            DEV cout << "  query has more, cursorid: " << cursorid << endl;
-                                            cc->matcher = matcher;
-                                            cc->ns = ns;
-                                            cc->pos = n;
-                                            cc->filter = filter;
-                                            cc->originalMessage = message;
-                                            cc->updateLocation();
+                    if( explain ) {
+                        n++;
+                    }
+                    else {
+                        bool ok = fillQueryResultFromObj(b, filter.get(), js);
+                        if( ok ) n++;
+                        if( ok ) {
+                            if( (ntoreturn>0 && (n >= ntoreturn || b.len() > MaxBytesToReturnToClientAtOnce)) ||
+                                (ntoreturn==0 && (b.len()>1*1024*1024 || n>=101)) ) {
+                                    /* if ntoreturn is zero, we return up to 101 objects.  on the subsequent getmore, there 
+                                    is only a size limit.  The idea is that on a find() where one doesn't use much results, 
+                                    we don't return much, but once getmore kicks in, we start pushing significant quantities.
+
+                                    The n limit (vs. size) is important when someone fetches only one small field from big 
+                                    objects, which causes massive scanning server-side.
+                                    */
+                                    /* if only 1 requested, no cursor saved for efficiency...we assume it is findOne() */
+                                    if( wantMore && ntoreturn != 1 ) {
+                                        if( useCursors ) {
+                                            c->advance();
+                                            if( c->ok() ) {
+                                                // more...so save a cursor
+                                                ClientCursor *cc = new ClientCursor();
+                                                cc->c = c;
+                                                cursorid = cc->cursorid;
+                                                DEV cout << "  query has more, cursorid: " << cursorid << endl;
+                                                cc->matcher = matcher;
+                                                cc->ns = ns;
+                                                cc->pos = n;
+                                                cc->filter = filter;
+                                                cc->originalMessage = message;
+                                                cc->updateLocation();
+                                            }
                                         }
                                     }
-                                }
-                                break;
+                                    break;
+                            }
                         }
                     }
                 }
@@ -693,8 +711,17 @@ QueryResult* runQuery(Message& message, const char *ns, int ntoskip, int _ntoret
 			c->advance();
 		} // end while
 
-		if( ordering ) { 
-			so->fill(b, filter.get(), n);
+        if( explain ) {
+            BSONObjBuilder builder;
+            builder.append("cursor", c->toString());
+            builder.append("nscanned", nscanned);
+            builder.append("n", n);
+            if( ordering ) 
+                builder.append("scanAndOrder", true);
+            BSONObj obj = builder.done();
+            fillQueryResultFromObj(b, 0, obj);
+        } else if( ordering ) { 
+            so->fill(b, filter.get(), n);
 		}
 		else if( cursorid == 0 && (queryOptions & Option_CursorTailable) && c->tailable() ) { 
 			c->setAtTail();
diff --git a/db/queryoptimizer.cpp b/db/queryoptimizer.cpp
new file mode 100644
index 00000000000..c01d31c0007
--- /dev/null
+++ b/db/queryoptimizer.cpp
@@ -0,0 +1,44 @@
+/* queryoptimizer.cpp */

+

+/**
+*    Copyright (C) 2008 10gen Inc.
+*  
+*    This program is free software: you can redistribute it and/or  modify
+*    it under the terms of the GNU Affero General Public License, version 3,
+*    as published by the Free Software Foundation.
+*  
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU Affero General Public License for more details.
+*  
+*    You should have received a copy of the GNU Affero General Public License
+*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "stdafx.h"
+#include "query.h"
+#include "pdfile.h"
+#include "jsobj.h"
+#include "../util/builder.h"
+#include <time.h>
+#include "btree.h"
+#include "../util/lruishmap.h"
+#include "json.h"
+#include "repl.h"
+#include "replset.h"
+#include "scanandorder.h"
+#include "queryoptimizer.h"
+
+QueryPlan QueryOptimizer::getPlan(
+        const char *ns,
+        BSONObj* query,
+        BSONObj* order,
+        BSONObj* hint) 
+{
+    QueryPlan plan;
+
+
+
+    return plan;
+}
diff --git a/db/queryoptimizer.h b/db/queryoptimizer.h
new file mode 100644
index 00000000000..86963039d83
--- /dev/null
+++ b/db/queryoptimizer.h
@@ -0,0 +1,49 @@
+/* queryoptimizer.h */

+

+/**
+*    Copyright (C) 2008 10gen Inc.
+*  
+*    This program is free software: you can redistribute it and/or  modify
+*    it under the terms of the GNU Affero General Public License, version 3,
+*    as published by the Free Software Foundation.
+*  
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU Affero General Public License for more details.
+*  
+*    You should have received a copy of the GNU Affero General Public License
+*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once 
+
+class QueryPlan { 
+public:
+    QueryPlan() { 
+        scanAndOrderRequired = false;
+        simpleKeyMatch = false;
+    }
+
+    auto_ptr<Cursor> cursor;
+
+    /* ScanAndOrder processing will be required if true */
+    bool scanAndOrderRequired;
+
+    /* When true, the index we are using has keys such that it can completely resolve the 
+       query expression to match by itself without ever checking the main object.
+       */
+    bool simpleKeyMatch;
+};
+
+/* We put these objects inside the Client objects: that way later if we want to do 
+   stats, it's in the right place.
+*/
+class QueryOptimizer { 
+public:
+    QueryPlan getPlan(
+        const char *ns,
+        BSONObj* query,
+        BSONObj* order = 0,
+        BSONObj* hint = 0);
+};
diff --git a/db/scanandorder.h b/db/scanandorder.h
index 941e597314e..f046b6cc925 100644
--- a/db/scanandorder.h
+++ b/db/scanandorder.h
@@ -1,4 +1,22 @@
-// scanandorder.h
+/* scanandorder.h
+   Order results (that aren't already indexes and in order.)
+*/
+
+/**
+*    Copyright (C) 2008 10gen Inc.
+*  
+*    This program is free software: you can redistribute it and/or  modify
+*    it under the terms of the GNU Affero General Public License, version 3,
+*    as published by the Free Software Foundation.
+*  
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU Affero General Public License for more details.
+*  
+*    You should have received a copy of the GNU Affero General Public License
+*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
 
 #pragma once