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// Contains helpers for checking, based on the explain output, properties of a
// plan. For instance, there are helpers for checking whether a plan is a collection
// scan or whether the plan is covered (index only).
load("jstests/libs/fixture_helpers.js"); // For FixtureHelpers.
/**
* Given the root stage of explain's JSON representation of a query plan ('root'), returns all
* subdocuments whose stage is 'stage'. Returns an empty array if the plan does not have the
* requested stage.
*/
function getPlanStages(root, stage) {
var results = [];
if (root.stage === stage) {
results.push(root);
}
if ("inputStage" in root) {
results = results.concat(getPlanStages(root.inputStage, stage));
}
if ("inputStages" in root) {
for (var i = 0; i < root.inputStages.length; i++) {
results = results.concat(getPlanStages(root.inputStages[i], stage));
}
}
if ("shards" in root) {
for (var i = 0; i < root.shards.length; i++) {
if ("winningPlan" in root.shards[i]) {
results = results.concat(getPlanStages(root.shards[i].winningPlan, stage));
} else {
results = results.concat(getPlanStages(root.shards[i].executionStages, stage));
}
}
}
return results;
}
/**
* Given the root stage of explain's JSON representation of a query plan ('root'), returns the
* subdocument with its stage as 'stage'. Returns null if the plan does not have such a stage.
* Asserts that no more than one stage is a match.
*/
function getPlanStage(root, stage) {
var planStageList = getPlanStages(root, stage);
if (planStageList.length === 0) {
return null;
} else {
assert(planStageList.length === 1,
"getPlanStage expects to find 0 or 1 matching stages. planStageList: " +
tojson(planStageList));
return planStageList[0];
}
}
/**
* Returns the set of rejected plans from the given replset or sharded explain output.
*/
function getRejectedPlans(root) {
if (root.queryPlanner.winningPlan.hasOwnProperty("shards")) {
const rejectedPlans = [];
for (let shard of root.queryPlanner.winningPlan.shards) {
for (let rejectedPlan of shard.rejectedPlans) {
rejectedPlans.push(Object.assign({shardName: shard.shardName}, rejectedPlan));
}
}
return rejectedPlans;
}
return root.queryPlanner.rejectedPlans;
}
/**
* Given the root stage of explain's JSON representation of a query plan ('root'), returns true if
* the query planner reports at least one rejected alternative plan, and false otherwise.
*/
function hasRejectedPlans(root) {
function sectionHasRejectedPlans(explainSection) {
assert(explainSection.hasOwnProperty("rejectedPlans"), tojson(explainSection));
return explainSection.rejectedPlans.length !== 0;
}
function cursorStageHasRejectedPlans(cursorStage) {
assert(cursorStage.hasOwnProperty("$cursor"), tojson(cursorStage));
assert(cursorStage.$cursor.hasOwnProperty("queryPlanner"), tojson(cursorStage));
return sectionHasRejectedPlans(cursorStage.$cursor.queryPlanner);
}
if (root.hasOwnProperty("shards")) {
// This is a sharded agg explain.
const cursorStages = getAggPlanStages(root, "$cursor");
assert(cursorStages.length !== 0, "Did not find any $cursor stages in sharded agg explain");
return cursorStages.find((cursorStage) => cursorStageHasRejectedPlans(cursorStage)) !==
undefined;
} else if (root.hasOwnProperty("stages")) {
// This is an agg explain.
const cursorStages = getAggPlanStages(root, "$cursor");
return cursorStages.find((cursorStage) => cursorStageHasRejectedPlans(cursorStage)) !==
undefined;
} else {
// This is some sort of query explain.
assert(root.hasOwnProperty("queryPlanner"), tojson(root));
assert(root.queryPlanner.hasOwnProperty("winningPlan"), tojson(root));
if (!root.queryPlanner.winningPlan.hasOwnProperty("shards")) {
// This is an unsharded explain.
return sectionHasRejectedPlans(root.queryPlanner);
}
// This is a sharded explain. Each entry in the shards array contains a 'winningPlan' and
// 'rejectedPlans'.
return root.queryPlanner.winningPlan.shards.find(
(shard) => sectionHasRejectedPlans(shard)) !== undefined;
}
}
/**
* Returns an array of execution stages from the given replset or sharded explain output.
*/
function getExecutionStages(root) {
if (root.executionStats.executionStages.hasOwnProperty("shards")) {
const executionStages = [];
for (let shard of root.executionStats.executionStages.shards) {
executionStages.push(Object.assign(
{shardName: shard.shardName, executionSuccess: shard.executionSuccess},
shard.executionStages));
}
return executionStages;
}
return [root.executionStats.executionStages];
}
/**
* Given the root stage of agg explain's JSON representation of a query plan ('root'), returns all
* subdocuments whose stage is 'stage'. This can either be an agg stage name like "$cursor" or
* "$sort", or a query stage name like "IXSCAN" or "SORT".
*
* Returns an empty array if the plan does not have the requested stage. Asserts that agg explain
* structure matches expected format.
*/
function getAggPlanStages(root, stage) {
let results = [];
function getDocumentSources(docSourceArray) {
let results = [];
for (let i = 0; i < docSourceArray.length; i++) {
let properties = Object.getOwnPropertyNames(docSourceArray[i]);
assert.eq(1, properties.length);
if (properties[0] === stage) {
results.push(docSourceArray[i]);
}
}
return results;
}
function getStagesFromInsideCursorStage(cursorStage) {
let results = [];
assert(cursorStage.hasOwnProperty("queryPlanner"));
assert(cursorStage.queryPlanner.hasOwnProperty("winningPlan"));
// If execution stats are available, then use the execution stats tree. Otherwise use the
// plan info from the "queryPlanner" section.
if (cursorStage.hasOwnProperty("executionStats")) {
assert(cursorStage.executionStats.hasOwnProperty("executionStages"));
results =
results.concat(getPlanStages(cursorStage.executionStats.executionStages, stage));
} else {
results = results.concat(getPlanStages(cursorStage.queryPlanner.winningPlan, stage));
}
return results;
}
if (root.hasOwnProperty("stages")) {
assert(root.stages.constructor === Array);
results = results.concat(getDocumentSources(root.stages));
if (root.stages[0].hasOwnProperty("$cursor")) {
results = results.concat(getStagesFromInsideCursorStage(root.stages[0].$cursor));
}
}
if (root.hasOwnProperty("shards")) {
for (let elem in root.shards) {
assert(root.shards[elem].stages.constructor === Array);
results = results.concat(getDocumentSources(root.shards[elem].stages));
const firstStage = root.shards[elem].stages[0];
if (firstStage.hasOwnProperty("$cursor")) {
results = results.concat(getStagesFromInsideCursorStage(firstStage.$cursor));
}
}
}
return results;
}
/**
* Given the root stage of agg explain's JSON representation of a query plan ('root'), returns the
* subdocument with its stage as 'stage'. Returns null if the plan does not have such a stage.
* Asserts that no more than one stage is a match.
*/
function getAggPlanStage(root, stage) {
let planStageList = getAggPlanStages(root, stage);
if (planStageList.length === 0) {
return null;
} else {
assert.eq(1,
planStageList.length,
"getAggPlanStage expects to find 0 or 1 matching stages. planStageList: " +
tojson(planStageList));
return planStageList[0];
}
}
/**
* Given the root stage of agg explain's JSON representation of a query plan ('root'), returns
* whether the plan as stage called 'stage'.
*/
function aggPlanHasStage(root, stage) {
return getAggPlanStage(root, stage) !== null;
}
/**
* Given the root stage of explain's BSON representation of a query plan ('root'),
* returns true if the plan has a stage called 'stage'.
*/
function planHasStage(db, root, stage) {
const matchingStages = getPlanStages(root, stage);
// If we are executing against a mongos, we may get more than one occurrence of the stage.
if (FixtureHelpers.isMongos(db)) {
return matchingStages.length >= 1;
} else {
assert.lt(matchingStages.length,
2,
`Expected to find 0 or 1 matching stages: ${tojson(matchingStages)}`);
return matchingStages.length === 1;
}
}
/**
* A query is covered iff it does *not* have a FETCH stage or a COLLSCAN.
*
* Given the root stage of explain's BSON representation of a query plan ('root'),
* returns true if the plan is index only. Otherwise returns false.
*/
function isIndexOnly(db, root) {
return !planHasStage(db, root, "FETCH") && !planHasStage(db, root, "COLLSCAN");
}
/**
* Returns true if the BSON representation of a plan rooted at 'root' is using
* an index scan, and false otherwise.
*/
function isIxscan(db, root) {
return planHasStage(db, root, "IXSCAN");
}
/**
* Returns true if the BSON representation of a plan rooted at 'root' is using
* the idhack fast path, and false otherwise.
*/
function isIdhack(db, root) {
return planHasStage(db, root, "IDHACK");
}
/**
* Returns true if the BSON representation of a plan rooted at 'root' is using
* a collection scan, and false otherwise.
*/
function isCollscan(db, root) {
return planHasStage(db, root, "COLLSCAN");
}
/**
* Get the number of chunk skips for the BSON exec stats tree rooted at 'root'.
*/
function getChunkSkips(root) {
if (root.stage === "SHARDING_FILTER") {
return root.chunkSkips;
} else if ("inputStage" in root) {
return getChunkSkips(root.inputStage);
} else if ("inputStages" in root) {
var skips = 0;
for (var i = 0; i < root.inputStages.length; i++) {
skips += getChunkSkips(root.inputStages[0]);
}
return skips;
}
return 0;
}
/**
* Given explain output at executionStats level verbosity, confirms that the root stage is COUNT or
* RECORD_STORE_FAST_COUNT and that the result of the count is equal to 'expectedCount'.
*/
function assertExplainCount({explainResults, expectedCount}) {
const execStages = explainResults.executionStats.executionStages;
// If passed through mongos, then the root stage should be the mongos SINGLE_SHARD stage or
// SHARD_MERGE stages, with COUNT as the root stage on each shard. If explaining directly on the
// shard, then COUNT is the root stage.
if ("SINGLE_SHARD" == execStages.stage || "SHARD_MERGE" == execStages.stage) {
let totalCounted = 0;
for (let shardExplain of execStages.shards) {
const countStage = shardExplain.executionStages;
assert(countStage.stage === "COUNT" || countStage.stage === "RECORD_STORE_FAST_COUNT",
"root stage on shard is not COUNT or RECORD_STORE_FAST_COUNT");
totalCounted += countStage.nCounted;
}
assert.eq(totalCounted, expectedCount, "wrong count result");
} else {
assert(execStages.stage === "COUNT" || execStages.stage === "RECORD_STORE_FAST_COUNT",
"root stage on shard is not COUNT or RECORD_STORE_FAST_COUNT");
assert.eq(execStages.nCounted, expectedCount, "wrong count result");
}
}
/**
* Verifies that a given query uses an index and is covered when used in a count command.
*/
function assertCoveredQueryAndCount({collection, query, project, count}) {
let explain = collection.find(query, project).explain();
assert(isIndexOnly(db, explain.queryPlanner.winningPlan),
"Winning plan was not covered: " + tojson(explain.queryPlanner.winningPlan));
// Same query as a count command should also be covered.
explain = collection.explain("executionStats").find(query).count();
assert(isIndexOnly(db, explain.queryPlanner.winningPlan),
"Winning plan for count was not covered: " + tojson(explain.queryPlanner.winningPlan));
assertExplainCount({explainResults: explain, expectedCount: count});
}
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