Imported Upstream version 2.6.11upstream/2.6.11

1 files changed, 230 insertions, 0 deletions

diff --git a/src/mongo/db/exec/fetch.cpp b/src/mongo/db/exec/fetch.cpp
new file mode 100644
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+++ b/src/mongo/db/exec/fetch.cpp
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+/**
+ *    Copyright (C) 2013 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/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/db/exec/fetch.h"
+
+#include "mongo/db/exec/filter.h"
+#include "mongo/db/exec/working_set_common.h"
+#include "mongo/db/pdfile.h"
+#include "mongo/util/fail_point_service.h"
+
+namespace mongo {
+
+    // Some fail points for testing.
+    MONGO_FP_DECLARE(fetchInMemoryFail);
+    MONGO_FP_DECLARE(fetchInMemorySucceed);
+
+    FetchStage::FetchStage(WorkingSet* ws, PlanStage* child, const MatchExpression* filter)
+        : _ws(ws), _child(child), _filter(filter), _idBeingPagedIn(WorkingSet::INVALID_ID) { }
+
+    FetchStage::~FetchStage() { }
+
+    bool FetchStage::isEOF() {
+        if (WorkingSet::INVALID_ID != _idBeingPagedIn) {
+            // We asked our parent for a page-in but he didn't get back to us.  We still need to
+            // return the result that _idBeingPagedIn refers to.
+            return false;
+        }
+
+        return _child->isEOF();
+    }
+
+    bool recordInMemory(const char* data) {
+        if (MONGO_FAIL_POINT(fetchInMemoryFail)) {
+            return false;
+        }
+
+        if (MONGO_FAIL_POINT(fetchInMemorySucceed)) {
+            return true;
+        }
+
+        return Record::likelyInPhysicalMemory(data);
+    }
+
+    PlanStage::StageState FetchStage::work(WorkingSetID* out) {
+        ++_commonStats.works;
+
+        if (isEOF()) { return PlanStage::IS_EOF; }
+
+        // If we asked our parent for a page-in last time work(...) was called, finish the fetch.
+        if (WorkingSet::INVALID_ID != _idBeingPagedIn) {
+            return fetchCompleted(out);
+        }
+
+        // If we're here, we're not waiting for a DiskLoc to be fetched.  Get another to-be-fetched
+        // result from our child.
+        WorkingSetID id = WorkingSet::INVALID_ID;
+        StageState status = _child->work(&id);
+
+        if (PlanStage::ADVANCED == status) {
+            WorkingSetMember* member = _ws->get(id);
+
+            // If there's an obj there, there is no fetching to perform.
+            if (member->hasObj()) {
+                ++_specificStats.alreadyHasObj;
+                return returnIfMatches(member, id, out);
+            }
+
+            // We need a valid loc to fetch from and this is the only state that has one.
+            verify(WorkingSetMember::LOC_AND_IDX == member->state);
+            verify(member->hasLoc());
+
+            Record* record = member->loc.rec();
+            const char* data = record->dataNoThrowing();
+
+            if (!recordInMemory(data)) {
+                // member->loc points to a record that's NOT in memory.  Pass a fetch request up.
+                verify(WorkingSet::INVALID_ID == _idBeingPagedIn);
+                _idBeingPagedIn = id;
+                *out = id;
+                ++_commonStats.needFetch;
+                return PlanStage::NEED_FETCH;
+            }
+            else {
+                // Don't need index data anymore as we have an obj.
+                member->keyData.clear();
+                member->obj = BSONObj(data);
+                member->state = WorkingSetMember::LOC_AND_UNOWNED_OBJ;
+                return returnIfMatches(member, id, out);
+            }
+        }
+        else if (PlanStage::FAILURE == status) {
+            *out = id;
+            // If a stage fails, it may create a status WSM to indicate why it
+            // failed, in which case 'id' is valid.  If ID is invalid, we
+            // create our own error message.
+            if (WorkingSet::INVALID_ID == id) {
+                mongoutils::str::stream ss;
+                ss << "fetch stage failed to read in results from child";
+                Status status(ErrorCodes::InternalError, ss);
+                *out = WorkingSetCommon::allocateStatusMember( _ws, status);
+            }
+            return status;
+        }
+        else {
+            if (PlanStage::NEED_FETCH == status) {
+                *out = id;
+                ++_commonStats.needFetch;
+            }
+            else if (PlanStage::NEED_TIME == status) {
+                ++_commonStats.needTime;
+            }
+            return status;
+        }
+    }
+
+    void FetchStage::prepareToYield() {
+        ++_commonStats.yields;
+        _child->prepareToYield();
+    }
+
+    void FetchStage::recoverFromYield() {
+        ++_commonStats.unyields;
+        _child->recoverFromYield();
+    }
+
+    void FetchStage::invalidate(const DiskLoc& dl, InvalidationType type) {
+        ++_commonStats.invalidates;
+
+        _child->invalidate(dl, type);
+
+        // If we're holding on to an object that we're waiting for the runner to page in...
+        if (WorkingSet::INVALID_ID != _idBeingPagedIn) {
+            // And we haven't already invalidated it...
+            WorkingSetMember* member = _ws->get(_idBeingPagedIn);
+            if (member->hasLoc() && (member->loc == dl)) {
+                // Just fetch it now and kill the DiskLoc.
+                WorkingSetCommon::fetchAndInvalidateLoc(member);
+            }
+        }
+    }
+
+    PlanStage::StageState FetchStage::fetchCompleted(WorkingSetID* out) {
+        WorkingSetMember* member = _ws->get(_idBeingPagedIn);
+
+        // The DiskLoc we're waiting to page in was invalidated (forced fetch).  Test for
+        // matching and maybe pass it up.
+        if (member->state == WorkingSetMember::OWNED_OBJ) {
+            WorkingSetID memberID = _idBeingPagedIn;
+            _idBeingPagedIn = WorkingSet::INVALID_ID;
+            return returnIfMatches(member, memberID, out);
+        }
+
+        // Assume that the caller has fetched appropriately.
+        // TODO: Do we want to double-check the runner?  Not sure how reliable likelyInMemory is
+        // on all platforms.
+        verify(member->hasLoc());
+        verify(!member->hasObj());
+
+        // Make the (unowned) object.
+        Record* record = member->loc.rec();
+        const char* data = record->dataNoThrowing();
+        member->obj = BSONObj(data);
+
+        // Don't need index data anymore as we have an obj.
+        member->keyData.clear();
+        member->state = WorkingSetMember::LOC_AND_UNOWNED_OBJ;
+        verify(!member->obj.isOwned());
+
+        // Return the obj if it passes our filter.
+        WorkingSetID memberID = _idBeingPagedIn;
+        _idBeingPagedIn = WorkingSet::INVALID_ID;
+        return returnIfMatches(member, memberID, out);
+    }
+
+    PlanStage::StageState FetchStage::returnIfMatches(WorkingSetMember* member,
+                                                      WorkingSetID memberID,
+                                                      WorkingSetID* out) {
+        if (Filter::passes(member, _filter)) {
+            if (NULL != _filter) {
+                ++_specificStats.matchTested;
+            }
+
+            *out = memberID;
+
+            ++_commonStats.advanced;
+            return PlanStage::ADVANCED;
+        }
+        else {
+            _ws->free(memberID);
+
+            ++_commonStats.needTime;
+            return PlanStage::NEED_TIME;
+        }
+    }
+
+    PlanStageStats* FetchStage::getStats() {
+        _commonStats.isEOF = isEOF();
+
+        auto_ptr<PlanStageStats> ret(new PlanStageStats(_commonStats, STAGE_FETCH));
+        ret->specific.reset(new FetchStats(_specificStats));
+        ret->children.push_back(_child->getStats());
+        return ret.release();
+    }
+
+}  // namespace mongo