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// @tags: [requires_non_retryable_writes, requires_fastcount]
// Tests for explaining the delete command.
(function() {
"use strict";
var collName = "jstests_explain_delete";
var t = db[collName];
t.drop();
var explain;
/**
* Verify that the explain command output 'explain' shows a DELETE stage with an nWouldDelete
* value equal to 'nWouldDelete'.
*/
function checkNWouldDelete(explain, nWouldDelete) {
assert.commandWorked(explain);
assert("executionStats" in explain);
var executionStats = explain.executionStats;
assert("executionStages" in executionStats);
// If passed through mongos, then DELETE stage(s) should be below the SHARD_WRITE mongos
// stage. Otherwise the DELETE stage is the root stage.
var execStages = executionStats.executionStages;
if ("SHARD_WRITE" === execStages.stage) {
let totalToBeDeletedAcrossAllShards = 0;
execStages.shards.forEach(function(shardExplain) {
const rootStageName = shardExplain.executionStages.stage;
assert.eq(rootStageName, "DELETE", tojson(execStages));
totalToBeDeletedAcrossAllShards += shardExplain.executionStages.nWouldDelete;
});
assert.eq(totalToBeDeletedAcrossAllShards, nWouldDelete, explain);
} else {
assert.eq(execStages.stage, "DELETE", explain);
assert.eq(execStages.nWouldDelete, nWouldDelete, explain);
}
}
// Explain delete against an empty collection.
assert.commandWorked(db.createCollection(t.getName()));
explain = db.runCommand({explain: {delete: collName, deletes: [{q: {a: 1}, limit: 0}]}});
checkNWouldDelete(explain, 0);
// Add an index but no data, and check that the explain still works.
t.ensureIndex({a: 1});
explain = db.runCommand({explain: {delete: collName, deletes: [{q: {a: 1}, limit: 0}]}});
checkNWouldDelete(explain, 0);
// Add some copies of the same document.
for (var i = 0; i < 10; i++) {
t.insert({a: 1});
}
assert.eq(10, t.count());
// Run an explain which shows that all 10 documents *would* be deleted.
explain = db.runCommand({explain: {delete: collName, deletes: [{q: {a: 1}, limit: 0}]}});
checkNWouldDelete(explain, 10);
// Make sure all 10 documents are still there.
assert.eq(10, t.count());
// If we run the same thing without the explain, then all 10 docs should be deleted.
var deleteResult = db.runCommand({delete: collName, deletes: [{q: {a: 1}, limit: 0}]});
assert.commandWorked(deleteResult);
assert.eq(0, t.count());
}());
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