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  1. Core Server
  2. SERVER-56084

[SBE] aggregation_multiversion_fuzzer fails with SBE on due to different results from $graphLookup

    • Type: Icon: Bug Bug
    • Resolution: Duplicate
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: None
    • Component/s: Query Execution
    • None
    • ALL
    • Hide
      python3 buildscripts/resmoke.py run --suites=jstestfuzz --additionalFeatureFlags=featureFlagSBE repro.js
      
      Show
      python3 buildscripts/resmoke.py run --suites=jstestfuzz --additionalFeatureFlags=featureFlagSBE repro.js
    • Query Execution 2021-04-19

      I've attached a repro script, which is just the generated test trimmed down to make it run much faster. The generated test came from this failing task. The offending query is the following:

      [js_test:agg_fuzzer-8818-1618157020929-0] 	"command" : {
      [js_test:agg_fuzzer-8818-1618157020929-0] 		"aggregate" : "fuzzer_coll",
      [js_test:agg_fuzzer-8818-1618157020929-0] 		"pipeline" : [
      [js_test:agg_fuzzer-8818-1618157020929-0] 			{
      [js_test:agg_fuzzer-8818-1618157020929-0] 				"$sort" : {
      [js_test:agg_fuzzer-8818-1618157020929-0] 					"_id" : 1
      [js_test:agg_fuzzer-8818-1618157020929-0] 				}
      [js_test:agg_fuzzer-8818-1618157020929-0] 			},
      [js_test:agg_fuzzer-8818-1618157020929-0] 			{
      [js_test:agg_fuzzer-8818-1618157020929-0] 				"$limit" : 20
      [js_test:agg_fuzzer-8818-1618157020929-0] 			},
      [js_test:agg_fuzzer-8818-1618157020929-0] 			{
      [js_test:agg_fuzzer-8818-1618157020929-0] 				"$graphLookup" : {
      [js_test:agg_fuzzer-8818-1618157020929-0] 					"from" : "fuzzer_coll",
      [js_test:agg_fuzzer-8818-1618157020929-0] 					"startWith" : {
      [js_test:agg_fuzzer-8818-1618157020929-0] 						"$setUnion" : [
      [js_test:agg_fuzzer-8818-1618157020929-0] 							[
      [js_test:agg_fuzzer-8818-1618157020929-0] 								/Dobra/
      [js_test:agg_fuzzer-8818-1618157020929-0] 							],
      [js_test:agg_fuzzer-8818-1618157020929-0] 							"$array",
      [js_test:agg_fuzzer-8818-1618157020929-0] 							"$obj.obj.obj.obj.array"
      [js_test:agg_fuzzer-8818-1618157020929-0] 						]
      [js_test:agg_fuzzer-8818-1618157020929-0] 					},
      [js_test:agg_fuzzer-8818-1618157020929-0] 					"connectFromField" : "obj.obj.obj.obj.obj.obj",
      [js_test:agg_fuzzer-8818-1618157020929-0] 					"connectToField" : "obj.obj.obj.obj.date",
      [js_test:agg_fuzzer-8818-1618157020929-0] 					"as" : "array",
      [js_test:agg_fuzzer-8818-1618157020929-0] 					"depthField" : "obj.obj.num",
      [js_test:agg_fuzzer-8818-1618157020929-0] 					"restrictSearchWithMatch" : {
      [js_test:agg_fuzzer-8818-1618157020929-0] 						"$or" : [
      [js_test:agg_fuzzer-8818-1618157020929-0] 							{
      [js_test:agg_fuzzer-8818-1618157020929-0] 								"obj.obj.obj.num" : {
      [js_test:agg_fuzzer-8818-1618157020929-0] 									"$not" : {
      [js_test:agg_fuzzer-8818-1618157020929-0] 										"$bitsAnyClear" : 1001
      [js_test:agg_fuzzer-8818-1618157020929-0] 									}
      [js_test:agg_fuzzer-8818-1618157020929-0] 								}
      [js_test:agg_fuzzer-8818-1618157020929-0] 							}
      [js_test:agg_fuzzer-8818-1618157020929-0] 						]
      [js_test:agg_fuzzer-8818-1618157020929-0] 					}
      [js_test:agg_fuzzer-8818-1618157020929-0] 				}
      [js_test:agg_fuzzer-8818-1618157020929-0] 			}
      [js_test:agg_fuzzer-8818-1618157020929-0] 		],
      [js_test:agg_fuzzer-8818-1618157020929-0] 		"maxTimeMS" : 30000,
      [js_test:agg_fuzzer-8818-1618157020929-0] 		"cursor" : {
      [js_test:agg_fuzzer-8818-1618157020929-0] 
      [js_test:agg_fuzzer-8818-1618157020929-0] 		},
      [js_test:agg_fuzzer-8818-1618157020929-0] 		"$db" : "fuzzer"
      

      Interestingly, due to SERVER-56083, the query does not run using SBE in either the control (4.4) or experimental (5.0) versions. I suspect, however, that the queries executed recursively by $graphLookup end up using SBE, which is where things have gone wrong.

      Looking at the output from the fuzzer, I can see that both servers returned 20 documents with the same _id values. However, none of the 20 documents returned by 4.4 were equal to any of the documents returned by 5.0. Drilling down, I looked specifically at the documents returned by each version with _id:0. I can see that the only difference between the two is the "array" field, which is what is produced by the $graphLookup stage.

      For the document with _id:0, I dumped the contents of "array" from the lefthand-side server into a collection called "l" and the contents of "array" from the righthand-side server into a collection called "r", and this shows that the lengths of the arrays were different:

      MongoDB Enterprise > db.l.count()
      190
      MongoDB Enterprise > db.r.count()
      188
      

      I believe this means that a few documents were missed by the $graphLookup when SBE was enabled. The following query shows exactly which were missed, specifically for the $graphLookup associated with _id:0:

      MongoDB Enterprise > db.l.aggregate([{$lookup: {from: "r", as: "match", localField: "_id", foreignField: "_id"}}, {$match: {match: {$size: 0}}}]).pretty()
      {
      	"_id" : 1078,
      	"str" : "orchid",
      	"num" : NumberLong(2178),
      	"date" : ISODate("2019-04-22T20:50:00.826Z"),
      	"array" : [
      		NumberLong(32525),
      		NumberLong(44047),
      		ISODate("2019-06-13T02:41:44.348Z"),
      		"Tools",
      		"Grove Product",
      		28213,
      		ISODate("2019-03-13T20:33:11.273Z"),
      		ISODate("2019-09-15T05:04:20.672Z"),
      		ISODate("2019-11-11T06:16:33.307Z"),
      		{
      			"_id" : 1079,
      			"str" : "Georgia Iraqi Dinar Lead",
      			"num" : 69643,
      			"date" : NaN,
      			"obj" : {
      				"_id" : 1080,
      				"str" : "generate THX virtual",
      				"num" : NumberLong(94448),
      				"array" : [
      					NumberDecimal("-643.826448748712"),
      					[ ],
      					NumberDecimal("272.28819709550726"),
      					null,
      					"e-tailers Mission"
      				],
      				"obj" : {
      					"_id" : 1081,
      					"str" : "envisioneer evolve Forks",
      					"num" : NumberDecimal("-397.33322040453436"),
      					"date" : ISODate("2019-07-05T14:28:07.010Z"),
      					"obj" : {
      
      					}
      				}
      			}
      		}
      	],
      	"obj" : {
      		"_id" : 1082,
      		"str" : "Intranet",
      		"num" : 74811,
      		"array" : [
      			{
      				"_id" : 1083,
      				"date" : ISODate("2019-05-15T16:46:30.286Z"),
      				"array" : [
      					{
      						"_id" : 1084,
      						"str" : null,
      						"num" : 20959,
      						"date" : null,
      						"array" : [ ],
      						"obj" : {
      
      						}
      					},
      					null,
      					NaN,
      					ISODate("2019-05-13T14:55:24.201Z")
      				]
      			}
      		],
      		"obj" : {
      			"_id" : 1085,
      			"array" : [
      				66718,
      				"back-end intangible",
      				[
      					"Multi-tiered turquoise Credit Card Account",
      					NumberDecimal("-4.27904291615323"),
      					{
      						"_id" : 1086,
      						"date" : ISODate("2019-10-15T15:08:13.433Z"),
      						"array" : [ ]
      					}
      				]
      			],
      			"obj" : {
      				"_id" : 1087,
      				"num" : NumberDecimal("-740.555235767481"),
      				"date" : ISODate("2019-11-23T19:12:50.139Z")
      			},
      			"num" : NumberLong(0)
      		}
      	},
      	"match" : [ ]
      }
      {
      	"_id" : 469,
      	"str" : "Tasty Rubber Pizza Bond Markets Units European Composite Unit (EURCO) robust",
      	"num" : NumberLong(81616),
      	"date" : ISODate("2019-08-05T01:32:15.829Z"),
      	"array" : [
      		ISODate("2019-01-28T14:08:07.624Z"),
      		"New Jersey Consultant",
      		23767,
      		72540,
      		ISODate("2019-12-28T19:30:44.661Z"),
      		NumberLong(32526),
      		"SQL",
      		[ ],
      		[ ],
      		75037
      	],
      	"obj" : {
      		"_id" : 470,
      		"str" : "Checking Account",
      		"num" : NumberLong(79901),
      		"date" : ISODate("2019-02-14T12:40:50.831Z"),
      		"array" : [
      			"CSS navigate Singapore",
      			null,
      			{
      				"_id" : 471,
      				"str" : "quantify",
      				"num" : NumberDecimal("-793.7706100048798"),
      				"date" : ISODate("2019-02-20T16:39:48.120Z"),
      				"array" : [
      					NaN,
      					NaN
      				],
      				"obj" : {
      					"_id" : 472,
      					"obj" : {
      						"_id" : 473,
      						"num" : 29622,
      						"date" : ISODate("2019-09-20T13:10:23.122Z"),
      						"array" : [
      							null,
      							ISODate("2019-10-15T02:26:25.924Z"),
      							[ ]
      						],
      						"obj" : {
      
      						}
      					}
      				}
      			}
      		],
      		"obj" : {
      			"_id" : 474,
      			"date" : NaN,
      			"array" : [ ],
      			"obj" : {
      				"_id" : 475,
      				"str" : "Mobility",
      				"num" : NumberDecimal("217.89759387808635")
      			},
      			"num" : NumberLong(0)
      		}
      	},
      	"match" : [ ]
      }
      

            Assignee:
            david.storch@mongodb.com David Storch
            Reporter:
            david.storch@mongodb.com David Storch
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              Created:
              Updated:
              Resolved: