N1QL query slow

pipo · November 1, 2016, 8:09am

Hi,
I imported IP2Country database from http://software77.net/geo-ip/ to my Couchbase bucket. Total documents is about ~ 160k.
Example document:

{
  "IPFrom": 1000083456,
  "IPTo": 1000085503,
  "Registry": "apnic",
  "Assigned": 1100736000,
  "Ctry": "JP",
  "Cntry": "JPN",
  "Country": "Japan",
  "_type": "ip2c"
}

I created 2 GSI index:
CREATE INDEX doc_type_idx ON default(_type) WHERE _type is not missing
and:
CREATE INDEX ip2c_idx ON default(_type,IPFrom,IPTo) WHERE _type = "ip2c"
Then run this query:
SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 AND IPTo >= 3627730286 LIMIT 1
It took ~ 9s
If remove IPTo >= 3627730286:
SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 LIMIT 1
It took only 14ms
What need i do to optimize the first query?

geraldss · November 1, 2016, 2:21pm

Can you post the EXPLAIN for both queries.

pipo · November 1, 2016, 2:56pm

EXPLAIN SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 AND IPTo >= 3627730286 LIMIT 1

[
  {
    "plan": {
      "#operator": "Sequence",
      "~children": [
        {
          "#operator": "Sequence",
          "~children": [
            {
              "#operator": "IndexScan",
              "index": "ip2c_idx",
              "index_id": "a3c9181d02b34c43",
              "keyspace": "default",
              "namespace": "default",
              "spans": [
                {
                  "Range": {
                    "High": [
                      "\"ip2c\"",
                      "successor(3627730286)"
                    ],
                    "Inclusion": 0,
                    "Low": [
                      "\"ip2c\"",
                      "null",
                      "3627730286"
                    ]
                  }
                }
              ],
              "using": "gsi"
            },
            {
              "#operator": "Fetch",
              "keyspace": "default",
              "namespace": "default"
            },
            {
              "#operator": "Parallel",
              "~child": {
                "#operator": "Sequence",
                "~children": [
                  {
                    "#operator": "Filter",
                    "condition": "((((`default`.`_type`) = \"ip2c\") and ((`default`.`IPFrom`) <= 3627730286)) and (3627730286 <= (`default`.`IPTo`)))"
                  },
                  {
                    "#operator": "InitialProject",
                    "result_terms": [
                      {
                        "expr": "(`default`.`Ctry`)"
                      }
                    ]
                  },
                  {
                    "#operator": "FinalProject"
                  }
                ]
              }
            }
          ]
        },
        {
          "#operator": "Limit",
          "expr": "1"
        }
      ]
    },
    "text": "SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 AND IPTo >= 3627730286 LIMIT 1"
  }
]

EXPLAIN SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 LIMIT 1

[
  {
    "plan": {
      "#operator": "Sequence",
      "~children": [
        {
          "#operator": "Sequence",
          "~children": [
            {
              "#operator": "IndexScan",
              "index": "ip2c_idx",
              "index_id": "a3c9181d02b34c43",
              "keyspace": "default",
              "limit": "1",
              "namespace": "default",
              "spans": [
                {
                  "Range": {
                    "High": [
                      "\"ip2c\"",
                      "successor(3627730286)"
                    ],
                    "Inclusion": 0,
                    "Low": [
                      "\"ip2c\"",
                      "null"
                    ]
                  }
                }
              ],
              "using": "gsi"
            },
            {
              "#operator": "Fetch",
              "keyspace": "default",
              "namespace": "default"
            },
            {
              "#operator": "Parallel",
              "~child": {
                "#operator": "Sequence",
                "~children": [
                  {
                    "#operator": "Filter",
                    "condition": "(((`default`.`_type`) = \"ip2c\") and ((`default`.`IPFrom`) <= 3627730286))"
                  },
                  {
                    "#operator": "InitialProject",
                    "result_terms": [
                      {
                        "expr": "(`default`.`Ctry`)"
                      }
                    ]
                  },
                  {
                    "#operator": "FinalProject"
                  }
                ]
              }
            }
          ]
        },
        {
          "#operator": "Limit",
          "expr": "1"
        }
      ]
    },
    "text": "SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 LIMIT 1"
  }
]

geraldss · November 1, 2016, 3:53pm

The second query is able to push the LIMIT down to the index. You can add IPFrom >= 0 to the first query.

If you also want to fetch more than one or a few documents, you can add Ctry as the last key in the index, which will make it a covering index.

pipo · November 1, 2016, 4:05pm

Thanks for quick reply.
Try to add IPFrom > 0 to query but it still took ~9s. Explain:

[
  {
    "plan": {
      "#operator": "Sequence",
      "~children": [
        {
          "#operator": "Sequence",
          "~children": [
            {
              "#operator": "IndexScan",
              "index": "ip2c_idx",
              "index_id": "a3c9181d02b34c43",
              "keyspace": "default",
              "namespace": "default",
              "spans": [
                {
                  "Range": {
                    "High": [
                      "\"ip2c\"",
                      "successor(3627730286)"
                    ],
                    "Inclusion": 0,
                    "Low": [
                      "\"ip2c\"",
                      "0",
                      "3627730286"
                    ]
                  }
                }
              ],
              "using": "gsi"
            },
            {
              "#operator": "Fetch",
              "keyspace": "default",
              "namespace": "default"
            },
            {
              "#operator": "Parallel",
              "~child": {
                "#operator": "Sequence",
                "~children": [
                  {
                    "#operator": "Filter",
                    "condition": "(((((`default`.`_type`) = \"ip2c\") and ((`default`.`IPFrom`) <= 3627730286)) and (0 < (`default`.`IPFrom`))) and (3627730286 <= (`default`.`IPTo`)))"
                  },
                  {
                    "#operator": "InitialProject",
                    "result_terms": [
                      {
                        "expr": "(`default`.`Ctry`)"
                      }
                    ]
                  },
                  {
                    "#operator": "FinalProject"
                  }
                ]
              }
            }
          ]
        },
        {
          "#operator": "Limit",
          "expr": "1"
        }
      ]
    },
    "text": "SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 AND IPFrom > 0 AND IPTo >= 3627730286 LIMIT 1"
  }
]

geraldss · November 1, 2016, 4:12pm

Sorry about that. What is the maximum value of IPTo?

Please add IPTo <= max value of IPTo

pipo · November 1, 2016, 4:23pm

Try both:
SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 AND IPFrom > 0 AND IPTo >= 3627730286 and IPTo <= 4294967295 LIMIT 1
and
SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 AND IPTo >= 3627730286 and IPTo <= 4294967295 LIMIT 1
It’s still the same above . Explain:

[
  {
    "plan": {
      "#operator": "Sequence",
      "~children": [
        {
          "#operator": "Sequence",
          "~children": [
            {
              "#operator": "IndexScan",
              "index": "ip2c_idx",
              "index_id": "a3c9181d02b34c43",
              "keyspace": "default",
              "namespace": "default",
              "spans": [
                {
                  "Range": {
                    "High": [
                      "\"ip2c\"",
                      "3627730286",
                      "4294967295"
                    ],
                    "Inclusion": 2,
                    "Low": [
                      "\"ip2c\"",
                      "0",
                      "3627730286"
                    ]
                  }
                }
              ],
              "using": "gsi"
            },
            {
              "#operator": "Fetch",
              "keyspace": "default",
              "namespace": "default"
            },
            {
              "#operator": "Parallel",
              "~child": {
                "#operator": "Sequence",
                "~children": [
                  {
                    "#operator": "Filter",
                    "condition": "((((((`default`.`_type`) = \"ip2c\") and ((`default`.`IPFrom`) <= 3627730286)) and (0 < (`default`.`IPFrom`))) and (3627730286 <= (`default`.`IPTo`))) and ((`default`.`IPTo`) <= 4294967295))"
                  },
                  {
                    "#operator": "InitialProject",
                    "result_terms": [
                      {
                        "expr": "(`default`.`Ctry`)"
                      }
                    ]
                  },
                  {
                    "#operator": "FinalProject"
                  }
                ]
              }
            }
          ]
        },
        {
          "#operator": "Limit",
          "expr": "1"
        }
      ]
    },
    "text": "SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 AND IPFrom > 0 AND IPTo >= 3627730286 and IPTo <= 4294967295 LIMIT 1"
  }
]

geraldss · November 1, 2016, 4:30pm

Are you using 4.5.1?

@vsr1, how do we push this LIMIT down to the indexer? Do we have to use a subquery?

pipo · November 1, 2016, 4:31pm

Yes, i’m using CB Server 4.5.1.

vsr1 · November 1, 2016, 4:47pm

The limit can be pushed to indexer when the predicates are exactly pushed to indexer and applying predicates by N1QL will not eliminate any items.

The IPFrom and IPTo are range predicates and will not qualifying pushing LIMIT.
You can use covering index to make it faster.
CREATE INDEX ip2c_idx ON default(_type,IPFrom,IPTo,Ctry) WHERE _type = “ip2c”;

pipo · November 1, 2016, 5:00pm

Use covering index, it took >3s to run the query. It seems not fast enough

geraldss · November 1, 2016, 5:10pm

Hi @vsr1,

This query is pushing down LIMIT. What is the difference?

SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 LIMIT 1

vsr1 · November 1, 2016, 5:23pm

Hi @geraldss,

_type=‘ip2c’ AND IPFrom <= 3627730286 has leading key is equal and second leading key is range (both low and high present). N1QL will not eliminate any items.

_type=‘ip2c’ AND IPFrom <= 3627730286 AND IPTo >= 3627730286 has leading key is equal and second leading key is range and third leading key is range. Indexer will generate false positives and N1QL can eliminate items and not able to push.

vsr1 · November 1, 2016, 5:28pm

3sec too long for LIMIT 1.
Could you use the following index and also post the EXPLAIN

CREATE INDEX ip2c_idx ON default(IPFrom,IPTo,Ctry) WHERE _type = “ip2c”;

pipo · November 1, 2016, 5:54pm

Explain:

[
  {
    "plan": {
      "#operator": "Sequence",
      "~children": [
        {
          "#operator": "Sequence",
          "~children": [
            {
              "#operator": "IndexScan",
              "covers": [
                "cover ((`default`.`_type`))",
                "cover ((`default`.`IPFrom`))",
                "cover ((`default`.`IPTo`))",
                "cover ((`default`.`Ctry`))",
                "cover ((meta(`default`).`id`))"
              ],
              "filter_covers": {
                "cover ((`default`.`_type`))": "ip2c"
              },
              "index": "ip2c_idx",
              "index_id": "21b9bddf92d0daf2",
              "keyspace": "default",
              "namespace": "default",
              "spans": [
                {
                  "Range": {
                    "High": [
                      "\"ip2c\"",
                      "successor(3627730286)"
                    ],
                    "Inclusion": 0,
                    "Low": [
                      "\"ip2c\"",
                      "null",
                      "3627730286"
                    ]
                  }
                }
              ],
              "using": "gsi"
            },
            {
              "#operator": "Parallel",
              "~child": {
                "#operator": "Sequence",
                "~children": [
                  {
                    "#operator": "Filter",
                    "condition": "(((cover ((`default`.`_type`)) = \"ip2c\") and (cover ((`default`.`IPFrom`)) <= 3627730286)) and (3627730286 <= cover ((`default`.`IPTo`))))"
                  },
                  {
                    "#operator": "InitialProject",
                    "result_terms": [
                      {
                        "expr": "cover ((`default`.`Ctry`))"
                      }
                    ]
                  },
                  {
                    "#operator": "FinalProject"
                  }
                ]
              }
            }
          ]
        },
        {
          "#operator": "Limit",
          "expr": "1"
        }
      ]
    },
    "text": "SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 AND IPTo >= 3627730286 LIMIT 1"
  }
]

vsr1 · November 1, 2016, 6:00pm

Could you please post the output of completed_requests for the Statement that matches your query only.

select * from system:completed_requests;

geraldss · November 1, 2016, 8:25pm

And how long does this query take with this index?

pipo · November 2, 2016, 1:27am

This is output of:
select * from system:completed_requests;

{
    "completed_requests": {
      "ClientContextID": "b50b35eb-0402-4aca-b23a-aa3b971a4f77",
      "ElapsedTime": "3.234391509s",
      "ErrorCount": 0,
      "PhaseCounts": {
        "IndexScan": 161922
      },
      "PhaseOperators": {
        "IndexScan": 1
      },
      "RequestId": "d00f4cec-d1de-4d27-bc81-786c83d692ee",
      "ResultCount": 1,
      "ResultSize": 36,
      "ServiceTime": "3.234343553s",
      "State": "completed",
      "Statement": "SELECT Ctry FROM default WHERE _type='ip2c' AND IPFrom <= 3627730286 AND IPTo >= 3627730286 LIMIT 1",
      "Time": "2016-11-02 01:26:49.366301201 +0000 UTC"
    }

Total documents is: 165434
Documents match IPFrom <= 3627730286: 161922
Documents match IPTo >= 3627730286: 3513
Query results(without LIMIT): 1
I don’t know why IndexScan = 161922

vsr1 · November 2, 2016, 12:04pm

try one of the following options:
Option 1)
CREATE INDEX ip2c_idx ON default(IPTo, IPFrom, Ctry) WHERE _type = “ip2c”;
SELECT Ctry FROM default WHERE _type=‘ip2c’ AND IPFrom <= 3627730286 AND IPTo >= 3627730286 LIMIT 1

OPTION 2)

CREATE INDEX ip2c_idx ON default(IPFrom,-IPTo,Ctry) WHERE _type = “ip2c”;
SELECT Ctry FROM default WHERE _type=‘ip2c’ AND IPFrom <= 3627730286 AND -IPTo <= -3627730286 LIMIT 1;

pipo · November 2, 2016, 2:52pm

The first option seems work, the query took ~150ms, but i think it doesn’t solve the problem. Suppose:
n1 is total documents that matches: IPFrom <= IP (IP is some value that need to be query)
n2 is total documents that matches: IPTo >= IP
idx1: default(IPTo, IPFrom, Ctry)
idx2: default(IPFrom, IPTo, Ctry)

If n1 >> n2 (significantly greater): query with idx1 will fast, idx2 will slow
n1 << n2: query with idx1 will slow, idx2 will fast
n1 ~ n2: the query will not too slow but still slow (about ~1s)

If create both idx1 and idx2, the CB server will select random index to run the query, I have use index hint, ex:
SELECT Ctry FROM default USE INDEX(idx1 USING GSI) WHERE _type='ip2c' AND IPTo >= 4294967295 AND IPFrom <=4294967295

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