SQL - EXPLAIN

Profiles any command and returns a JSON data on the result of its execution. You may find this useful to see why queries are running slow. Use it as a keyword before any command that you want to profile.

Syntax

  1. EXPLAIN <command>
  • <command> Defines the command that you want to profile.

Examples

  • Profile a query that executes on a class without indexes:

    1. orientdb> EXPLAIN SELECT FROM Account
    2.  
    3. Profiled command '{documentReads:1126, documentReadsCompatibleClass:1126, 
    4. recordReads:1126, elapsed:209, resultType:collection, resultSize:1126}' 
    5. in 0,212000 sec(s).

  • Profile a query that executes on a class with indexes:

    1. orientdb> EXPLAIN SELECT FROM Profile WHERE name = 'Luca'
    2.  
    3. Profiled command '{involvedIndexes:[1], indexReads:1, resultType:collection
    4. resultSize:1, documentAnalyzedCompatibleClass:1, elapsed:1}' 
    5. in 0,002000 sec(s).

For more information,s ee

Understanding the Profile

When you run this command, it returns JSON data containing all of the following profile metrics:

Metric Description
elapsed Time to execute in seconds. The precision is the nanosecond.
resultType The result-type: collection, document, or number.
resultSize Number of records retrieved, in cases where the result-type is collection.
recordReads Number of records read from disk.
documentReads Number of documents read from disk. This metric may differ from recordReads in the event that other kinds of records are present in the command target. For instance, if you have documents and recordbytes in the same cluster it may skip many records. That said, in case of scans, it is recommended that you store different records in separate clusters.
documentAnalyzedCompatibleClass Number of documents analyzed in the class. For instance, if you use the same cluster in documents for the classes Account and Invoice, it would skip records of the class Invoice when you target the class Account. In case of scans, it is recommended that you store different classes in separate clusters.
involvedIndexes Indexes involved in the command.
indexReads Number of records read from the index.