COUNT(*) or MAX(id) - which is faster?How to efficiently count the number of keys/properties of an object in JavaScript?Which “href” value should I use for JavaScript links, “#” or “javascript:void(0)”?Which is faster: Stack allocation or Heap allocationSQL select only rows with max value on a columnWhy are elementwise additions much faster in separate loops than in a combined loop?Why is it faster to process a sorted array than an unsorted array?Why does Python code run faster in a function?Is < faster than <=?Which is faster: while(1) or while(2)?Why is [] faster than list()?

Why doesn't a const reference extend the life of a temporary object passed via a function?

How to answer pointed "are you quitting" questioning when I don't want them to suspect

Landlord wants to switch my lease to a "Land contract" to "get back at the city"

Prime joint compound before latex paint?

Extreme, but not acceptable situation and I can't start the work tomorrow morning

Is there a familial term for apples and pears?

How is it possible for user's password to be changed after storage was encrypted? (on OS X, Android)

Are white and non-white police officers equally likely to kill black suspects?

I see my dog run

Symmetry in quantum mechanics

What happens when a metallic dragon and a chromatic dragon mate?

How did the USSR manage to innovate in an environment characterized by government censorship and high bureaucracy?

How to make particles emit from certain parts of a 3D object?

"My colleague's body is amazing"

How do I create uniquely male characters?

I’m planning on buying a laser printer but concerned about the life cycle of toner in the machine

Could a US political party gain complete control over the government by removing checks & balances?

LWC and complex parameters

Can I find out the caloric content of bread by dehydrating it?

Is there a way to make member function NOT callable from constructor?

What do the Banks children have against barley water?

COUNT(*) or MAX(id) - which is faster?

Was there ever an axiom rendered a theorem?

How to move the player while also allowing forces to affect it



COUNT(*) or MAX(id) - which is faster?


How to efficiently count the number of keys/properties of an object in JavaScript?Which “href” value should I use for JavaScript links, “#” or “javascript:void(0)”?Which is faster: Stack allocation or Heap allocationSQL select only rows with max value on a columnWhy are elementwise additions much faster in separate loops than in a combined loop?Why is it faster to process a sorted array than an unsorted array?Why does Python code run faster in a function?Is < faster than <=?Which is faster: while(1) or while(2)?Why is [] faster than list()?






.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty height:90px;width:728px;box-sizing:border-box;








9















i have a web server, that has my own messaging system implemented.
I am at phase, when i need to create API, that checks, if the user has new message(s).
My DB table is simple:



ID - Auto Increment, Primary Key (Bigint)
Sender - Varchar (32) // Foreign Key to UserID hash from Users DB Table
Recipient - Varchar (32) // Foreign Key to UserID hash from Users DB Table
Message - Varchar (256) //UTF8 BIN


I am considering to make an api, that will estimate, if there are new messages for given user. I am thinking to use one of these methods:



A) Select count(*) of messages where sender or recipient is me.

(if this number > previous number, I have new message)



B) Select max(ID) of messages where sender or recipient is me.

(if max(ID) > than previous number, I have new message)



My question is: Can i calculate somehow, what method will consume less server resources? Or is there some article? Maybe another method i not mentioned?










share|improve this question



















  • 2





    I think you would be better off by adding a timestamp column and checking against that value to see if there are newer records.

    – Dharman
    7 hours ago











  • Either querying a timestamp or the ID, use MAX() on that column, and make sure it's indexed with (user_id, timestamp).

    – The Impaler
    7 hours ago











  • @Dharman i was thinking of it. But it costs extra DB space, also i am not sure if it will be faster than one of my methods. I am storing the simple number (of current messages) in usernames table

    – FeHora
    7 hours ago






  • 1





    Calculate? No idea. But you can measure it. Fire off a few thousands of each query and watch machine metrics (cpu%, mem%, load average, etc.)

    – Sergio Tulentsev
    7 hours ago






  • 1





    While there is a good answer to this question below, I suspect you might be optimizing on something that turns out not to be important. And unless you anticipate having literally millions of messages, I wouldn't worry about disk space, especially because the timestamp is small compared to your other fields. If you add timestamps, your table will be about 5MB larger for each million messages. That's really nothing.

    – Jerry
    6 hours ago

















9















i have a web server, that has my own messaging system implemented.
I am at phase, when i need to create API, that checks, if the user has new message(s).
My DB table is simple:



ID - Auto Increment, Primary Key (Bigint)
Sender - Varchar (32) // Foreign Key to UserID hash from Users DB Table
Recipient - Varchar (32) // Foreign Key to UserID hash from Users DB Table
Message - Varchar (256) //UTF8 BIN


I am considering to make an api, that will estimate, if there are new messages for given user. I am thinking to use one of these methods:



A) Select count(*) of messages where sender or recipient is me.

(if this number > previous number, I have new message)



B) Select max(ID) of messages where sender or recipient is me.

(if max(ID) > than previous number, I have new message)



My question is: Can i calculate somehow, what method will consume less server resources? Or is there some article? Maybe another method i not mentioned?










share|improve this question



















  • 2





    I think you would be better off by adding a timestamp column and checking against that value to see if there are newer records.

    – Dharman
    7 hours ago











  • Either querying a timestamp or the ID, use MAX() on that column, and make sure it's indexed with (user_id, timestamp).

    – The Impaler
    7 hours ago











  • @Dharman i was thinking of it. But it costs extra DB space, also i am not sure if it will be faster than one of my methods. I am storing the simple number (of current messages) in usernames table

    – FeHora
    7 hours ago






  • 1





    Calculate? No idea. But you can measure it. Fire off a few thousands of each query and watch machine metrics (cpu%, mem%, load average, etc.)

    – Sergio Tulentsev
    7 hours ago






  • 1





    While there is a good answer to this question below, I suspect you might be optimizing on something that turns out not to be important. And unless you anticipate having literally millions of messages, I wouldn't worry about disk space, especially because the timestamp is small compared to your other fields. If you add timestamps, your table will be about 5MB larger for each million messages. That's really nothing.

    – Jerry
    6 hours ago













9












9








9


1






i have a web server, that has my own messaging system implemented.
I am at phase, when i need to create API, that checks, if the user has new message(s).
My DB table is simple:



ID - Auto Increment, Primary Key (Bigint)
Sender - Varchar (32) // Foreign Key to UserID hash from Users DB Table
Recipient - Varchar (32) // Foreign Key to UserID hash from Users DB Table
Message - Varchar (256) //UTF8 BIN


I am considering to make an api, that will estimate, if there are new messages for given user. I am thinking to use one of these methods:



A) Select count(*) of messages where sender or recipient is me.

(if this number > previous number, I have new message)



B) Select max(ID) of messages where sender or recipient is me.

(if max(ID) > than previous number, I have new message)



My question is: Can i calculate somehow, what method will consume less server resources? Or is there some article? Maybe another method i not mentioned?










share|improve this question
















i have a web server, that has my own messaging system implemented.
I am at phase, when i need to create API, that checks, if the user has new message(s).
My DB table is simple:



ID - Auto Increment, Primary Key (Bigint)
Sender - Varchar (32) // Foreign Key to UserID hash from Users DB Table
Recipient - Varchar (32) // Foreign Key to UserID hash from Users DB Table
Message - Varchar (256) //UTF8 BIN


I am considering to make an api, that will estimate, if there are new messages for given user. I am thinking to use one of these methods:



A) Select count(*) of messages where sender or recipient is me.

(if this number > previous number, I have new message)



B) Select max(ID) of messages where sender or recipient is me.

(if max(ID) > than previous number, I have new message)



My question is: Can i calculate somehow, what method will consume less server resources? Or is there some article? Maybe another method i not mentioned?







php mysql performance






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 2 hours ago









Peter Cordes

134k18203342




134k18203342










asked 7 hours ago









FeHoraFeHora

535




535







  • 2





    I think you would be better off by adding a timestamp column and checking against that value to see if there are newer records.

    – Dharman
    7 hours ago











  • Either querying a timestamp or the ID, use MAX() on that column, and make sure it's indexed with (user_id, timestamp).

    – The Impaler
    7 hours ago











  • @Dharman i was thinking of it. But it costs extra DB space, also i am not sure if it will be faster than one of my methods. I am storing the simple number (of current messages) in usernames table

    – FeHora
    7 hours ago






  • 1





    Calculate? No idea. But you can measure it. Fire off a few thousands of each query and watch machine metrics (cpu%, mem%, load average, etc.)

    – Sergio Tulentsev
    7 hours ago






  • 1





    While there is a good answer to this question below, I suspect you might be optimizing on something that turns out not to be important. And unless you anticipate having literally millions of messages, I wouldn't worry about disk space, especially because the timestamp is small compared to your other fields. If you add timestamps, your table will be about 5MB larger for each million messages. That's really nothing.

    – Jerry
    6 hours ago












  • 2





    I think you would be better off by adding a timestamp column and checking against that value to see if there are newer records.

    – Dharman
    7 hours ago











  • Either querying a timestamp or the ID, use MAX() on that column, and make sure it's indexed with (user_id, timestamp).

    – The Impaler
    7 hours ago











  • @Dharman i was thinking of it. But it costs extra DB space, also i am not sure if it will be faster than one of my methods. I am storing the simple number (of current messages) in usernames table

    – FeHora
    7 hours ago






  • 1





    Calculate? No idea. But you can measure it. Fire off a few thousands of each query and watch machine metrics (cpu%, mem%, load average, etc.)

    – Sergio Tulentsev
    7 hours ago






  • 1





    While there is a good answer to this question below, I suspect you might be optimizing on something that turns out not to be important. And unless you anticipate having literally millions of messages, I wouldn't worry about disk space, especially because the timestamp is small compared to your other fields. If you add timestamps, your table will be about 5MB larger for each million messages. That's really nothing.

    – Jerry
    6 hours ago







2




2





I think you would be better off by adding a timestamp column and checking against that value to see if there are newer records.

– Dharman
7 hours ago





I think you would be better off by adding a timestamp column and checking against that value to see if there are newer records.

– Dharman
7 hours ago













Either querying a timestamp or the ID, use MAX() on that column, and make sure it's indexed with (user_id, timestamp).

– The Impaler
7 hours ago





Either querying a timestamp or the ID, use MAX() on that column, and make sure it's indexed with (user_id, timestamp).

– The Impaler
7 hours ago













@Dharman i was thinking of it. But it costs extra DB space, also i am not sure if it will be faster than one of my methods. I am storing the simple number (of current messages) in usernames table

– FeHora
7 hours ago





@Dharman i was thinking of it. But it costs extra DB space, also i am not sure if it will be faster than one of my methods. I am storing the simple number (of current messages) in usernames table

– FeHora
7 hours ago




1




1





Calculate? No idea. But you can measure it. Fire off a few thousands of each query and watch machine metrics (cpu%, mem%, load average, etc.)

– Sergio Tulentsev
7 hours ago





Calculate? No idea. But you can measure it. Fire off a few thousands of each query and watch machine metrics (cpu%, mem%, load average, etc.)

– Sergio Tulentsev
7 hours ago




1




1





While there is a good answer to this question below, I suspect you might be optimizing on something that turns out not to be important. And unless you anticipate having literally millions of messages, I wouldn't worry about disk space, especially because the timestamp is small compared to your other fields. If you add timestamps, your table will be about 5MB larger for each million messages. That's really nothing.

– Jerry
6 hours ago





While there is a good answer to this question below, I suspect you might be optimizing on something that turns out not to be important. And unless you anticipate having literally millions of messages, I wouldn't worry about disk space, especially because the timestamp is small compared to your other fields. If you add timestamps, your table will be about 5MB larger for each million messages. That's really nothing.

– Jerry
6 hours ago












2 Answers
2






active

oldest

votes


















12














In MySQL InnoDB, SELECT COUNT(*) WHERE secondary_index = ? is an expensive operation and when the user has a lot of messages, this query might take a long time. Even when using an index, the engine still needs to count all matching records.



On the other hand, SELECT MAX(id) WHERE secondary_index = ? can deliver the highest id in that index very efficiently and runs in constant speed by doing a so-called loose index scan.



If you want to understand why, consider looking up the "B-Tree+" data structure which InnoDB uses to organise its data.



I suggest you go with SELECT MAX(id), if the requirement is only to check if there are new messages (and not the count of them).



Also, if you rely on the message count you might open a gap for race conditions. What if the user deletes a message and receives a new one between two polling intervals?






share|improve this answer

























  • refer: dba.stackexchange.com/questions/130780/mysql-count-performance

    – Kaii
    7 hours ago






  • 1





    "SELECT MAX(id) will always use the primary index" - yeah, except for the cases when there's a where on an unindexed field.

    – Sergio Tulentsev
    7 hours ago











  • @SergioTulentsev i forgot to mention in my main post, sender and recipient are foreign keys to user-hash (ID) - primary key in users table. So it will be indexed always.

    – FeHora
    7 hours ago







  • 3





    If there's an index on a, then SELECT MAX(id) FROM tbl WHERE a=constant uses a so-called loose index scan. Those are almost miraculously fast. SELECT COUNT(*) FROM tbl WHERE a=constant does a tight index scan, which is not as fast.

    – O. Jones
    6 hours ago







  • 1





    @FeHora i strongly suggest to setup some sort of test environment, a database with generated records for you to play with.

    – Kaii
    6 hours ago



















1














To have the information that someone has new messages - do exactly that. Update the field in users table (I'm assuming that's the name) when a new message is recorded in the system. You have the recipient's ID, that's all you need. You can create an after insert trigger (assumption: there's users2messages table) that updates users table with a boolean flag indicating there's a message.



This approach is by far faster than counting indexes, be the index primary or secondary. When the user performs an action, you can update the users table with has_messages = 0, when a new message arrives - you update the table with has_messages = 1. It's simple, it works, it scales and using triggers to maintain it makes it easy and seamless.
I'm sure there will be nay-sayers who don't like triggers, you can do it manually at the point of associating a user with a new message.






share|improve this answer























  • triggers aside, looking up a row using the PK and also reading it to check the boolean is still more expensive than executing a single loose index scan. It gets worse when you also add a WHERE clause to check the boolean flag because of the low cardinality even if you index that field. Sorry to tell you you that, but you have a misunderstanding there.

    – Kaii
    6 hours ago












  • @Mjh i know about that.. but it's definitely more expensive than my suggested methods, because it contains (at least) 1x update + 1x select

    – FeHora
    6 hours ago






  • 1





    @Kaii SELECT has_messages FROM users WHERE id = 1; is the fastest query there is. It's an eq_ref which is infinitely faster than counting a number of records in the table. The boolean field is not in the WHERE clause, the primary key is. Please, assume better next time. In regards to updating the table: the update is fast as well, it handles a single row located using the primary key. If the field is already containing the value that you're updating to, no actual disk I/O occurs and there's a minimal performance penalty. Much less than counting the records. You can measure.

    – Mjh
    5 hours ago












Your Answer






StackExchange.ifUsing("editor", function ()
StackExchange.using("externalEditor", function ()
StackExchange.using("snippets", function ()
StackExchange.snippets.init();
);
);
, "code-snippets");

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "1"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);



);













draft saved

draft discarded


















StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55581114%2fcount-or-maxid-which-is-faster%23new-answer', 'question_page');

);

Post as a guest















Required, but never shown

























2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









12














In MySQL InnoDB, SELECT COUNT(*) WHERE secondary_index = ? is an expensive operation and when the user has a lot of messages, this query might take a long time. Even when using an index, the engine still needs to count all matching records.



On the other hand, SELECT MAX(id) WHERE secondary_index = ? can deliver the highest id in that index very efficiently and runs in constant speed by doing a so-called loose index scan.



If you want to understand why, consider looking up the "B-Tree+" data structure which InnoDB uses to organise its data.



I suggest you go with SELECT MAX(id), if the requirement is only to check if there are new messages (and not the count of them).



Also, if you rely on the message count you might open a gap for race conditions. What if the user deletes a message and receives a new one between two polling intervals?






share|improve this answer

























  • refer: dba.stackexchange.com/questions/130780/mysql-count-performance

    – Kaii
    7 hours ago






  • 1





    "SELECT MAX(id) will always use the primary index" - yeah, except for the cases when there's a where on an unindexed field.

    – Sergio Tulentsev
    7 hours ago











  • @SergioTulentsev i forgot to mention in my main post, sender and recipient are foreign keys to user-hash (ID) - primary key in users table. So it will be indexed always.

    – FeHora
    7 hours ago







  • 3





    If there's an index on a, then SELECT MAX(id) FROM tbl WHERE a=constant uses a so-called loose index scan. Those are almost miraculously fast. SELECT COUNT(*) FROM tbl WHERE a=constant does a tight index scan, which is not as fast.

    – O. Jones
    6 hours ago







  • 1





    @FeHora i strongly suggest to setup some sort of test environment, a database with generated records for you to play with.

    – Kaii
    6 hours ago
















12














In MySQL InnoDB, SELECT COUNT(*) WHERE secondary_index = ? is an expensive operation and when the user has a lot of messages, this query might take a long time. Even when using an index, the engine still needs to count all matching records.



On the other hand, SELECT MAX(id) WHERE secondary_index = ? can deliver the highest id in that index very efficiently and runs in constant speed by doing a so-called loose index scan.



If you want to understand why, consider looking up the "B-Tree+" data structure which InnoDB uses to organise its data.



I suggest you go with SELECT MAX(id), if the requirement is only to check if there are new messages (and not the count of them).



Also, if you rely on the message count you might open a gap for race conditions. What if the user deletes a message and receives a new one between two polling intervals?






share|improve this answer

























  • refer: dba.stackexchange.com/questions/130780/mysql-count-performance

    – Kaii
    7 hours ago






  • 1





    "SELECT MAX(id) will always use the primary index" - yeah, except for the cases when there's a where on an unindexed field.

    – Sergio Tulentsev
    7 hours ago











  • @SergioTulentsev i forgot to mention in my main post, sender and recipient are foreign keys to user-hash (ID) - primary key in users table. So it will be indexed always.

    – FeHora
    7 hours ago







  • 3





    If there's an index on a, then SELECT MAX(id) FROM tbl WHERE a=constant uses a so-called loose index scan. Those are almost miraculously fast. SELECT COUNT(*) FROM tbl WHERE a=constant does a tight index scan, which is not as fast.

    – O. Jones
    6 hours ago







  • 1





    @FeHora i strongly suggest to setup some sort of test environment, a database with generated records for you to play with.

    – Kaii
    6 hours ago














12












12








12







In MySQL InnoDB, SELECT COUNT(*) WHERE secondary_index = ? is an expensive operation and when the user has a lot of messages, this query might take a long time. Even when using an index, the engine still needs to count all matching records.



On the other hand, SELECT MAX(id) WHERE secondary_index = ? can deliver the highest id in that index very efficiently and runs in constant speed by doing a so-called loose index scan.



If you want to understand why, consider looking up the "B-Tree+" data structure which InnoDB uses to organise its data.



I suggest you go with SELECT MAX(id), if the requirement is only to check if there are new messages (and not the count of them).



Also, if you rely on the message count you might open a gap for race conditions. What if the user deletes a message and receives a new one between two polling intervals?






share|improve this answer















In MySQL InnoDB, SELECT COUNT(*) WHERE secondary_index = ? is an expensive operation and when the user has a lot of messages, this query might take a long time. Even when using an index, the engine still needs to count all matching records.



On the other hand, SELECT MAX(id) WHERE secondary_index = ? can deliver the highest id in that index very efficiently and runs in constant speed by doing a so-called loose index scan.



If you want to understand why, consider looking up the "B-Tree+" data structure which InnoDB uses to organise its data.



I suggest you go with SELECT MAX(id), if the requirement is only to check if there are new messages (and not the count of them).



Also, if you rely on the message count you might open a gap for race conditions. What if the user deletes a message and receives a new one between two polling intervals?







share|improve this answer














share|improve this answer



share|improve this answer








edited 6 hours ago

























answered 7 hours ago









KaiiKaii

15.7k22951




15.7k22951












  • refer: dba.stackexchange.com/questions/130780/mysql-count-performance

    – Kaii
    7 hours ago






  • 1





    "SELECT MAX(id) will always use the primary index" - yeah, except for the cases when there's a where on an unindexed field.

    – Sergio Tulentsev
    7 hours ago











  • @SergioTulentsev i forgot to mention in my main post, sender and recipient are foreign keys to user-hash (ID) - primary key in users table. So it will be indexed always.

    – FeHora
    7 hours ago







  • 3





    If there's an index on a, then SELECT MAX(id) FROM tbl WHERE a=constant uses a so-called loose index scan. Those are almost miraculously fast. SELECT COUNT(*) FROM tbl WHERE a=constant does a tight index scan, which is not as fast.

    – O. Jones
    6 hours ago







  • 1





    @FeHora i strongly suggest to setup some sort of test environment, a database with generated records for you to play with.

    – Kaii
    6 hours ago


















  • refer: dba.stackexchange.com/questions/130780/mysql-count-performance

    – Kaii
    7 hours ago






  • 1





    "SELECT MAX(id) will always use the primary index" - yeah, except for the cases when there's a where on an unindexed field.

    – Sergio Tulentsev
    7 hours ago











  • @SergioTulentsev i forgot to mention in my main post, sender and recipient are foreign keys to user-hash (ID) - primary key in users table. So it will be indexed always.

    – FeHora
    7 hours ago







  • 3





    If there's an index on a, then SELECT MAX(id) FROM tbl WHERE a=constant uses a so-called loose index scan. Those are almost miraculously fast. SELECT COUNT(*) FROM tbl WHERE a=constant does a tight index scan, which is not as fast.

    – O. Jones
    6 hours ago







  • 1





    @FeHora i strongly suggest to setup some sort of test environment, a database with generated records for you to play with.

    – Kaii
    6 hours ago

















refer: dba.stackexchange.com/questions/130780/mysql-count-performance

– Kaii
7 hours ago





refer: dba.stackexchange.com/questions/130780/mysql-count-performance

– Kaii
7 hours ago




1




1





"SELECT MAX(id) will always use the primary index" - yeah, except for the cases when there's a where on an unindexed field.

– Sergio Tulentsev
7 hours ago





"SELECT MAX(id) will always use the primary index" - yeah, except for the cases when there's a where on an unindexed field.

– Sergio Tulentsev
7 hours ago













@SergioTulentsev i forgot to mention in my main post, sender and recipient are foreign keys to user-hash (ID) - primary key in users table. So it will be indexed always.

– FeHora
7 hours ago






@SergioTulentsev i forgot to mention in my main post, sender and recipient are foreign keys to user-hash (ID) - primary key in users table. So it will be indexed always.

– FeHora
7 hours ago





3




3





If there's an index on a, then SELECT MAX(id) FROM tbl WHERE a=constant uses a so-called loose index scan. Those are almost miraculously fast. SELECT COUNT(*) FROM tbl WHERE a=constant does a tight index scan, which is not as fast.

– O. Jones
6 hours ago






If there's an index on a, then SELECT MAX(id) FROM tbl WHERE a=constant uses a so-called loose index scan. Those are almost miraculously fast. SELECT COUNT(*) FROM tbl WHERE a=constant does a tight index scan, which is not as fast.

– O. Jones
6 hours ago





1




1





@FeHora i strongly suggest to setup some sort of test environment, a database with generated records for you to play with.

– Kaii
6 hours ago






@FeHora i strongly suggest to setup some sort of test environment, a database with generated records for you to play with.

– Kaii
6 hours ago














1














To have the information that someone has new messages - do exactly that. Update the field in users table (I'm assuming that's the name) when a new message is recorded in the system. You have the recipient's ID, that's all you need. You can create an after insert trigger (assumption: there's users2messages table) that updates users table with a boolean flag indicating there's a message.



This approach is by far faster than counting indexes, be the index primary or secondary. When the user performs an action, you can update the users table with has_messages = 0, when a new message arrives - you update the table with has_messages = 1. It's simple, it works, it scales and using triggers to maintain it makes it easy and seamless.
I'm sure there will be nay-sayers who don't like triggers, you can do it manually at the point of associating a user with a new message.






share|improve this answer























  • triggers aside, looking up a row using the PK and also reading it to check the boolean is still more expensive than executing a single loose index scan. It gets worse when you also add a WHERE clause to check the boolean flag because of the low cardinality even if you index that field. Sorry to tell you you that, but you have a misunderstanding there.

    – Kaii
    6 hours ago












  • @Mjh i know about that.. but it's definitely more expensive than my suggested methods, because it contains (at least) 1x update + 1x select

    – FeHora
    6 hours ago






  • 1





    @Kaii SELECT has_messages FROM users WHERE id = 1; is the fastest query there is. It's an eq_ref which is infinitely faster than counting a number of records in the table. The boolean field is not in the WHERE clause, the primary key is. Please, assume better next time. In regards to updating the table: the update is fast as well, it handles a single row located using the primary key. If the field is already containing the value that you're updating to, no actual disk I/O occurs and there's a minimal performance penalty. Much less than counting the records. You can measure.

    – Mjh
    5 hours ago
















1














To have the information that someone has new messages - do exactly that. Update the field in users table (I'm assuming that's the name) when a new message is recorded in the system. You have the recipient's ID, that's all you need. You can create an after insert trigger (assumption: there's users2messages table) that updates users table with a boolean flag indicating there's a message.



This approach is by far faster than counting indexes, be the index primary or secondary. When the user performs an action, you can update the users table with has_messages = 0, when a new message arrives - you update the table with has_messages = 1. It's simple, it works, it scales and using triggers to maintain it makes it easy and seamless.
I'm sure there will be nay-sayers who don't like triggers, you can do it manually at the point of associating a user with a new message.






share|improve this answer























  • triggers aside, looking up a row using the PK and also reading it to check the boolean is still more expensive than executing a single loose index scan. It gets worse when you also add a WHERE clause to check the boolean flag because of the low cardinality even if you index that field. Sorry to tell you you that, but you have a misunderstanding there.

    – Kaii
    6 hours ago












  • @Mjh i know about that.. but it's definitely more expensive than my suggested methods, because it contains (at least) 1x update + 1x select

    – FeHora
    6 hours ago






  • 1





    @Kaii SELECT has_messages FROM users WHERE id = 1; is the fastest query there is. It's an eq_ref which is infinitely faster than counting a number of records in the table. The boolean field is not in the WHERE clause, the primary key is. Please, assume better next time. In regards to updating the table: the update is fast as well, it handles a single row located using the primary key. If the field is already containing the value that you're updating to, no actual disk I/O occurs and there's a minimal performance penalty. Much less than counting the records. You can measure.

    – Mjh
    5 hours ago














1












1








1







To have the information that someone has new messages - do exactly that. Update the field in users table (I'm assuming that's the name) when a new message is recorded in the system. You have the recipient's ID, that's all you need. You can create an after insert trigger (assumption: there's users2messages table) that updates users table with a boolean flag indicating there's a message.



This approach is by far faster than counting indexes, be the index primary or secondary. When the user performs an action, you can update the users table with has_messages = 0, when a new message arrives - you update the table with has_messages = 1. It's simple, it works, it scales and using triggers to maintain it makes it easy and seamless.
I'm sure there will be nay-sayers who don't like triggers, you can do it manually at the point of associating a user with a new message.






share|improve this answer













To have the information that someone has new messages - do exactly that. Update the field in users table (I'm assuming that's the name) when a new message is recorded in the system. You have the recipient's ID, that's all you need. You can create an after insert trigger (assumption: there's users2messages table) that updates users table with a boolean flag indicating there's a message.



This approach is by far faster than counting indexes, be the index primary or secondary. When the user performs an action, you can update the users table with has_messages = 0, when a new message arrives - you update the table with has_messages = 1. It's simple, it works, it scales and using triggers to maintain it makes it easy and seamless.
I'm sure there will be nay-sayers who don't like triggers, you can do it manually at the point of associating a user with a new message.







share|improve this answer












share|improve this answer



share|improve this answer










answered 6 hours ago









MjhMjh

1,98911112




1,98911112












  • triggers aside, looking up a row using the PK and also reading it to check the boolean is still more expensive than executing a single loose index scan. It gets worse when you also add a WHERE clause to check the boolean flag because of the low cardinality even if you index that field. Sorry to tell you you that, but you have a misunderstanding there.

    – Kaii
    6 hours ago












  • @Mjh i know about that.. but it's definitely more expensive than my suggested methods, because it contains (at least) 1x update + 1x select

    – FeHora
    6 hours ago






  • 1





    @Kaii SELECT has_messages FROM users WHERE id = 1; is the fastest query there is. It's an eq_ref which is infinitely faster than counting a number of records in the table. The boolean field is not in the WHERE clause, the primary key is. Please, assume better next time. In regards to updating the table: the update is fast as well, it handles a single row located using the primary key. If the field is already containing the value that you're updating to, no actual disk I/O occurs and there's a minimal performance penalty. Much less than counting the records. You can measure.

    – Mjh
    5 hours ago


















  • triggers aside, looking up a row using the PK and also reading it to check the boolean is still more expensive than executing a single loose index scan. It gets worse when you also add a WHERE clause to check the boolean flag because of the low cardinality even if you index that field. Sorry to tell you you that, but you have a misunderstanding there.

    – Kaii
    6 hours ago












  • @Mjh i know about that.. but it's definitely more expensive than my suggested methods, because it contains (at least) 1x update + 1x select

    – FeHora
    6 hours ago






  • 1





    @Kaii SELECT has_messages FROM users WHERE id = 1; is the fastest query there is. It's an eq_ref which is infinitely faster than counting a number of records in the table. The boolean field is not in the WHERE clause, the primary key is. Please, assume better next time. In regards to updating the table: the update is fast as well, it handles a single row located using the primary key. If the field is already containing the value that you're updating to, no actual disk I/O occurs and there's a minimal performance penalty. Much less than counting the records. You can measure.

    – Mjh
    5 hours ago

















triggers aside, looking up a row using the PK and also reading it to check the boolean is still more expensive than executing a single loose index scan. It gets worse when you also add a WHERE clause to check the boolean flag because of the low cardinality even if you index that field. Sorry to tell you you that, but you have a misunderstanding there.

– Kaii
6 hours ago






triggers aside, looking up a row using the PK and also reading it to check the boolean is still more expensive than executing a single loose index scan. It gets worse when you also add a WHERE clause to check the boolean flag because of the low cardinality even if you index that field. Sorry to tell you you that, but you have a misunderstanding there.

– Kaii
6 hours ago














@Mjh i know about that.. but it's definitely more expensive than my suggested methods, because it contains (at least) 1x update + 1x select

– FeHora
6 hours ago





@Mjh i know about that.. but it's definitely more expensive than my suggested methods, because it contains (at least) 1x update + 1x select

– FeHora
6 hours ago




1




1





@Kaii SELECT has_messages FROM users WHERE id = 1; is the fastest query there is. It's an eq_ref which is infinitely faster than counting a number of records in the table. The boolean field is not in the WHERE clause, the primary key is. Please, assume better next time. In regards to updating the table: the update is fast as well, it handles a single row located using the primary key. If the field is already containing the value that you're updating to, no actual disk I/O occurs and there's a minimal performance penalty. Much less than counting the records. You can measure.

– Mjh
5 hours ago






@Kaii SELECT has_messages FROM users WHERE id = 1; is the fastest query there is. It's an eq_ref which is infinitely faster than counting a number of records in the table. The boolean field is not in the WHERE clause, the primary key is. Please, assume better next time. In regards to updating the table: the update is fast as well, it handles a single row located using the primary key. If the field is already containing the value that you're updating to, no actual disk I/O occurs and there's a minimal performance penalty. Much less than counting the records. You can measure.

– Mjh
5 hours ago


















draft saved

draft discarded
















































Thanks for contributing an answer to Stack Overflow!


  • Please be sure to answer the question. Provide details and share your research!

But avoid


  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.

To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55581114%2fcount-or-maxid-which-is-faster%23new-answer', 'question_page');

);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

Oświęcim Innehåll Historia | Källor | Externa länkar | Navigeringsmeny50°2′18″N 19°13′17″Ö / 50.03833°N 19.22139°Ö / 50.03833; 19.2213950°2′18″N 19°13′17″Ö / 50.03833°N 19.22139°Ö / 50.03833; 19.221393089658Nordisk familjebok, AuschwitzInsidan tro och existensJewish Community i OświęcimAuschwitz Jewish Center: MuseumAuschwitz Jewish Center

Valle di Casies Indice Geografia fisica | Origini del nome | Storia | Società | Amministrazione | Sport | Note | Bibliografia | Voci correlate | Altri progetti | Collegamenti esterni | Menu di navigazione46°46′N 12°11′E / 46.766667°N 12.183333°E46.766667; 12.183333 (Valle di Casies)46°46′N 12°11′E / 46.766667°N 12.183333°E46.766667; 12.183333 (Valle di Casies)Sito istituzionaleAstat Censimento della popolazione 2011 - Determinazione della consistenza dei tre gruppi linguistici della Provincia Autonoma di Bolzano-Alto Adige - giugno 2012Numeri e fattiValle di CasiesDato IstatTabella dei gradi/giorno dei Comuni italiani raggruppati per Regione e Provincia26 agosto 1993, n. 412Heraldry of the World: GsiesStatistiche I.StatValCasies.comWikimedia CommonsWikimedia CommonsValle di CasiesSito ufficialeValle di CasiesMM14870458910042978-6

Typsetting diagram chases (with TikZ?) Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)How to define the default vertical distance between nodes?Draw edge on arcNumerical conditional within tikz keys?TikZ: Drawing an arc from an intersection to an intersectionDrawing rectilinear curves in Tikz, aka an Etch-a-Sketch drawingLine up nested tikz enviroments or how to get rid of themHow to place nodes in an absolute coordinate system in tikzCommutative diagram with curve connecting between nodesTikz with standalone: pinning tikz coordinates to page cmDrawing a Decision Diagram with Tikz and layout manager