MongoDB Tutorial for Beginners 12 - MongoDB Indexing Video Lecture | The Complete Developers Guide to Mongo DB - Database Management

hello guys welcome to the next video on
MongoDB database tutorial for beginners
in this video we will see how and why we
use indexing in MongoDB so first of all
what are indexes indexes are the special
data structure that stores a small
portion of data set in the easy to pass
me now why we use indexes now indexes
supports the efficient resolution of
queries without indexes if you are
MongoDB database is really large for
example it has ten million documents and
you need to find one of the documents
it's really inefficient to find one
document out of 10 million or you know
millions and millions of data now
indexes make it easy to you know parse
this data if you want to use large
database now how to use indexes let's
see so first of all what I have done is
if you can see here I have created a
temporary database called temp and using
this for loop I have inserted 10 million
document in this database now to make
this database it will take some time to
insert these 10 million you know
documents that's why I have already you
know issued this command which already
created 10 million data for us now for
this video I'm going to use the normal
windows command prompt to see our result
better so I have opened the empty
command prompt and I'm going to just
give long go here and we are switched to
this shell and then we will switch to
our temp database so just right you
stamp then press ENTER switch to temp
and then let's print out the documents
first how these document looks so just
give DB dot
posts posts is the collection name in my
case you can see here right so this is
the post collection dot find and then
these brackets and press enter and what
it does is it's going to print the top
result for example to top 20 results and
it tell you to type I T for printing so
it's not going to print all the
10-million result using this command
line that's why I'm using this otherwise
if I give this command here it will be
really slow and the chef will try to
fetch all the 10 million documents which
we don't want right now right so now we
have 10 million documents so let's try
to find something and let's see how much
time it takes so I'm going to give the
same command and this time I'm going to
give some criteria here so for example
student I T we want to search for for
example student ID thousand okay and
let's see how much time it takes so I'm
going to press ENTER and you see it
takes time time and still searching and
it has searched with this result which
is thousand but it takes some time about
two seconds or as few seconds right
that's why we need indexing so whenever
we you know create indexing for some
elements of a document then it's going
to search for this document faster what
way of searching is is you can see if
you give find one command here so
instead of fine you just give find one
note this part like this find one and
press Enter
it finds it immediately because what
happens in fine one case is is going to
search for the student whose ID is
thousand and at the time it's search or
it finds this ID it immediately exits
but in the case of find it's going to
find all the document in all the
document which is matching student ID
are you know ten thousand so it's going
to see in all the ten million result for
this student ID thousand so let's create
by indexing and let's see how fast this
result becomes so to create an index for
a document what you can do is you can
just give the command DB and then the
collection name which is pose and then
you give insure index command so just
write dot en s you ar e insure index
okay and then in round brackets you just
give the key value pair so just give
these curly brackets and in the double
quotes for example you give a student ID
as your key so just give student ID here
and then just give coolin what okay so
it's going to do the indexing for this
element in all the documents and now we
are going to execute it so press enter
and you see it takes some time to create
the indexing of this and after this
indexing is created it will become
really fast when you want to search for
the same data again okay so if you do
this kind of indexing it will be really
fast and efficient to find your data
that's why we use indexing so now
indexing of our documents are done and
let's find this student ID once again so
I'm going to give this command DB post
dot find for the student by the thousand
let's give this time ten thousand or a
hundred thousand for example and let's
search for it so I'm going to press
Enter and immediately finds this
document so in case of this after
creating the indexing it becomes really
fast
search your document based upon the
index you have defined but be careful
while you're defining the index you
don't want to create the index for every
field you may want to create the index
where your IDs are unique for examples
for example in my case the student ID is
unique in this case so I have provided
this index so you may want to restrict
yourself while creating the indexes so
in this way you can create the index now
in order to remove our index how you can
remove my index so in order to remove an
index what you can do is you can give
the same command and instead of ensure
index you can just say drop index so
just write drop index okay and it's
going to drop your index so I'm going to
press ENTER and it says okay and once
again I'm going to find this student and
press ENTER now you see it takes time
few seconds and after searching for a
few seconds it will give the result so
in this way you can use indexes in
MongoDB I hope you enjoyed this video
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