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  • Database indexes - what should they be

    - by WebweaverD
    Most of my database tables have a clear unique index through which lookups are done 90% of the time but I am a bit unsure on this one - I have a table which keeps track of user rating totals for items in my database, I now want to add another table, to track individual ratings with an ip address column to make sure no one can rate something twice. Since I can see this becoming a big, high use table it is important to optimize it correctly. (MYSQL table) This table will have the following fields: rating_id(always - unique), item_id (always - not unique), user_id (optional - not unique), ip_address (always - not unique), rating_value(always - not unique), has_review(bool) Now I envisions 90% the queries going something like this: When a user rates something - select where item_id = x and ip_address = y, (if rows = 0) insert rating When in user account pages - select where ip_address = x or username = y Now none of the fields searched on are unique, can I still use them as indexes (for example item _id and ip_address), can I have two indexes and will this still improve performance over a non indexed table?

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  • need help optimizing oracle query

    - by deming
    I need help in optimizing the following query. It is taking a long time to finish. It takes almost 213 seconds . because of some constraints, I can not add an index and have to live with existing ones. INSERT INTO temp_table_1 ( USER_ID, role_id, participant_code, status_id ) WITH A AS (SELECT USER_ID user_id,ROLE_ID, STATUS_ID,participant_code FROM USER_ROLE WHERE participant_code IS NOT NULL), --1 B AS (SELECT ROLE_ID FROM CMP_ROLE WHERE GROUP_ID = 3), C AS (SELECT USER_ID FROM USER) --2 SELECT USER_ID,ROLE_ID,PARTICIPANT_CODE,MAX(STATUS_ID) FROM A INNER JOIN B USING (ROLE_ID) INNER JOIN C USING (USER_ID) GROUP BY USER_ID,role_id,participant_code ; --1 = query when ran alone takes 100+ seconds --2 = query when ran alone takes 19 seconds DELETE temp_table_1 WHERE ROWID NOT IN ( SELECT a.ROWID FROM temp_table_1 a, USER_ROLE b WHERE a.status_id = b.status_id AND ( b.ACTIVE IN ( 1 ) OR ( b.ACTIVE IN ( 0,3 ) AND SYSDATE BETWEEN b.effective_from_date AND b.effective_to_date )) ); It seems like the person who wrote the query is trying to get everything into a temp table first and then deleting records from the temp table. whatever is left is the actual results. Can't it be done such a way that there is no need for the delete? We just get the results needed since that will save time?

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  • How efficient is an if statement compared to a test that doesn't use an if? (C++)

    - by Keand64
    I need a program to get the smaller of two numbers, and I'm wondering if using a standard "if x is less than y" int a, b, low; if (a < b) low = a; else low = a; is more or less efficient than this: int a, b, low; low = b + ((a - b) & ((a - b) >> 31)); (or the variation of putting int delta = a - b at the top and rerplacing instances of a - b with that). I'm just wondering which one of these would be more efficient (or if the difference is to miniscule to be relevant), and the efficiency of if-else statements versus alternatives in general.

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  • Why is doing a top(1) on an indexed column in mssql slow?

    - by reinier
    I'm puzzled by the following. I have a DB with around 10 million rows, and (among other indices) on 1 column is an index. Now I have 700k rows where the campaignid is indeed 3835 For all these rows, the connectionid is the same. I just want to find out this connectionid. use messaging_db; SELECT TOP (1) connectionid FROM outgoing_messages WITH (NOLOCK) WHERE (campaignid_int = 3835) Now this query takes approx 30 seconds to perform! I (with my small db knowledge) would expect that it would take any of the rows, and return me that connectionid If I test this same query for a campaign which only has 1 entry, it goes really fast. So the index works. How would I tackle this and why does this not work?

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  • Is code clearness killing application performance?

    - by Jorge Córdoba
    As today's code is getting more complex by the minute, code needs to be designed to be maintainable - meaning easy to read, and easy to understand. That being said, I can't help but remember the programs that ran a couple of years ago such as Winamp or some games in which you needed a high performance program because your 486 100 Mhz wouldn't play mp3s with that beautiful mp3 player which consumed all of your CPU cycles. Now I run Media Player (or whatever), start playing an mp3 and it eats up a 25-30% of one of my four cores. Come on!! If a 486 can do it, how can the playback take up so much processor to do the same? I'm a developer myself, and I always used to advise: keep your code simple, don't prematurely optimize for performance. It seems that we've gone from "trying to get it to use the least amount of CPU as possible" to "if it doesn't take too much CPU is all right". So, do you think we are killing performance by ignoring optimizations?

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  • Python Profiling In Windows, How do you ignore Builtin Functions

    - by Tim McJilton
    I have not been capable of finding this anywhere online. I was looking to find out using a profiler how to better optimize my code, and when sorting by which functions use up the most time cumulatively, things like str(), print, and other similar widely used functions eat up much of the profile. What is the best way to profile a python program to get the user-defined functions only to see what areas of their code they can optimize? I hope that makes sense, any light you can shed on this subject would be very appreciated.

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  • Mysql slow query: INNER JOIN + ORDER BY causes filesort

    - by Alexander
    Hello! I'm trying to optimize this query: SELECT `posts`.* FROM `posts` INNER JOIN `posts_tags` ON `posts`.id = `posts_tags`.post_id WHERE (((`posts_tags`.tag_id = 1))) ORDER BY posts.created_at DESC; The size of tables is 38k rows, and 31k and mysql uses "filesort" so it gets pretty slow. I tried to use different indexes, no luck. CREATE TABLE `posts` ( `id` int(11) NOT NULL auto_increment, `created_at` datetime default NULL, PRIMARY KEY (`id`), KEY `index_posts_on_created_at` (`created_at`), KEY `for_tags` (`trashed`,`published`,`clan_private`,`created_at`) ) ENGINE=InnoDB AUTO_INCREMENT=44390 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci CREATE TABLE `posts_tags` ( `id` int(11) NOT NULL auto_increment, `post_id` int(11) default NULL, `tag_id` int(11) default NULL, `created_at` datetime default NULL, `updated_at` datetime default NULL, PRIMARY KEY (`id`), KEY `index_posts_tags_on_post_id_and_tag_id` (`post_id`,`tag_id`) ) ENGINE=InnoDB AUTO_INCREMENT=63175 DEFAULT CHARSET=utf8 +----+-------------+------------+--------+--------------------------+--------------------------+---------+---------------------+-------+-----------------------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+------------+--------+--------------------------+--------------------------+---------+---------------------+-------+-----------------------------------------------------------+ | 1 | SIMPLE | posts_tags | index | index_post_id_and_tag_id | index_post_id_and_tag_id | 10 | NULL | 24159 | Using where; Using index; Using temporary; Using filesort | | 1 | SIMPLE | posts | eq_ref | PRIMARY | PRIMARY | 4 | .posts_tags.post_id | 1 | | +----+-------------+------------+--------+--------------------------+--------------------------+---------+---------------------+-------+-----------------------------------------------------------+ 2 rows in set (0.00 sec) What kind of index I need to define to avoid mysql using filesort? Is it possible when order field is not in where clause?

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  • Ruby Challenge - efficiently change the last character of every word in a sentence to a capital

    - by emson
    Hi All I recently was challenged to write some Ruby code to change the last character of every word in a sentence into a capital. Such that the string: "script to convert the last letter of every word to a capital" becomes "scripT tO converT thE lasT letteR oF everY worD tO A capitaL" This was my optimal solution however I'm sure you wizards have much better solutions and I would be really interested to hear them. "script to convert the last letter of every word to a capital".split.map{|w|w<<w.slice!(-1).chr.upcase}.join' ' For those interested as to what is going on here is an explanation. split will split the sentence up into an array, the default delimiter is a space and with Ruby you don't need to use brackets here. map the array from split is passed to map which opens a block and process each word (w) in the array. the block slice!(s) off the last character of the word and converts it to a chr (a character not ASCII code) and then capitalises upcase it. This character is now appended << to the word which is missing the sliced last letter. Finally the array of words is now join together with a ' ' to reform the sentence. Enjoy

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  • Feedback on Optimizing C# NET Code Block

    - by Brett Powell
    I just spent quite a few hours reading up on TCP servers and my desired protocol I was trying to implement, and finally got everything working great. I noticed the code looks like absolute bollocks (is the the correct usage? Im not a brit) and would like some feedback on optimizing it, mostly for reuse and readability. The packet formats are always int, int, int, string, string. try { BinaryReader reader = new BinaryReader(clientStream); int packetsize = reader.ReadInt32(); int requestid = reader.ReadInt32(); int serverdata = reader.ReadInt32(); Console.WriteLine("Packet Size: {0} RequestID: {1} ServerData: {2}", packetsize, requestid, serverdata); List<byte> str = new List<byte>(); byte nextByte = reader.ReadByte(); while (nextByte != 0) { str.Add(nextByte); nextByte = reader.ReadByte(); } // Password Sent to be Authenticated string string1 = Encoding.UTF8.GetString(str.ToArray()); str.Clear(); nextByte = reader.ReadByte(); while (nextByte != 0) { str.Add(nextByte); nextByte = reader.ReadByte(); } // NULL string string string2 = Encoding.UTF8.GetString(str.ToArray()); Console.WriteLine("String1: {0} String2: {1}", string1, string2); // Reply to Authentication Request MemoryStream stream = new MemoryStream(); BinaryWriter writer = new BinaryWriter(stream); writer.Write((int)(1)); // Packet Size writer.Write((int)(requestid)); // Mirror RequestID if Authenticated, -1 if Failed byte[] buffer = stream.ToArray(); clientStream.Write(buffer, 0, buffer.Length); clientStream.Flush(); } I am going to be dealing with other packet types as well that are formatted the same (int/int/int/str/str), but different values. I could probably create a packet class, but this is a bit outside my scope of knowledge for how to apply it to this scenario. If it makes any difference, this is the Protocol I am implementing. http://developer.valvesoftware.com/wiki/Source_RCON_Protocol

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  • OpenGL Performance Questions

    - by Daniel
    This subject, as with any optimisation problem, gets hit on a lot, but I just couldn't find what I (think) I want. A lot of tutorials, and even SO questions have similar tips; generally covering: Use GL face culling (the OpenGL function, not the scene logic) Only send 1 matrix to the GPU (projectionModelView combination), therefore decreasing the MVP calculations from per vertex to once per model (as it should be). Use interleaved Vertices Minimize as many GL calls as possible, batch where appropriate And possibly a few/many others. I am (for curiosity reasons) rendering 28 million triangles in my application using several vertex buffers. I have tried all the above techniques (to the best of my knowledge), and received almost no performance change. Whilst I am receiving around 40FPS in my implementation, which is by no means problematic, I am still curious as to where these optimisation 'tips' actually come into use? My CPU is idling around 20-50% during rendering, therefore I assume I am GPU bound for increasing performance. Note: I am looking into gDEBugger at the moment Cross posted at Game Development

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  • Need help on nested loop of queries in php and mysql?

    - by mysqllearner
    Hi, I am trying to get do this: <?php $good_customer = 0; $q = mysql_query("SELECT user FROM users WHERE activated = '1'"); // this gives me about 40k users while($r = mysql_fetch_assoc($q)){ $money_spent = 0; $user = $r['user']; // Do queries on another 20 tables for($i = 1; $i<=20 ; $i++){ $tbl_name = 'data' . $i; $q2 = mysql_query("SELECT money_spent FROM $tbl_name WHERE user = '{$user}'"); while($r2 = mysql_fetch_assoc($q2)){ $money_spend += $r2['money_spent']; } if($money_spend > 1000000){ $good_customer += 1; } } } This is just an example. I am testing on localhost, for single user, it returns very fast. But when I try 1000, it takes forever, not even mentioned 40k users. Anyway to optimise/improve this code? EDIT: By the way, each of the others 20 tables has ~20 - 40k records

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  • Queries within queries: Is there a better way?

    - by mririgo
    As I build bigger, more advanced web applications, I'm finding myself writing extremely long and complex queries. I tend to write queries within queries a lot because I feel making one call to the database from PHP is better than making several and correlating the data. However, anyone who knows anything about SQL knows about JOINs. Personally, I've used a JOIN or two before, but quickly stopped when I discovered using subqueries because it felt easier and quicker for me to write and maintain. Commonly, I'll do subqueries that may contain one or more subqueries from relative tables. Consider this example: SELECT (SELECT username FROM users WHERE records.user_id = user_id) AS username, (SELECT last_name||', '||first_name FROM users WHERE records.user_id = user_id) AS name, in_timestamp, out_timestamp FROM records ORDER BY in_timestamp Rarely, I'll do subqueries after the WHERE clause. Consider this example: SELECT user_id, (SELECT name FROM organizations WHERE (SELECT organization FROM locations WHERE records.location = location_id) = organization_id) AS organization_name FROM records ORDER BY in_timestamp In these two cases, would I see any sort of improvement if I decided to rewrite the queries using a JOIN? As more of a blanket question, what are the advantages/disadvantages of using subqueries or a JOIN? Is one way more correct or accepted than the other?

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  • Building static (but complicated) lookup table using templates.

    - by MarkD
    I am currently in the process of optimizing a numerical analysis code. Within the code, there is a 200x150 element lookup table (currently a static std::vector < std::vector < double ) that is constructed at the beginning of every run. The construction of the lookup table is actually quite complex- the values in the lookup table are constructed using an iterative secant method on a complicated set of equations. Currently, for a simulation, the construction of the lookup table is 20% of the run time (run times are on the order of 25 second, lookup table construction takes 5 seconds). While 5-seconds might not seem to be a lot, when running our MC simulations, where we are running 50k+ simulations, it suddenly becomes a big chunk of time. Along with some other ideas, one thing that has been floated- can we construct this lookup table using templates at compile time? The table itself never changes. Hard-coding a large array isn't a maintainable solution (the equations that go into generating the table are constantly being tweaked), but it seems that if the table can be generated at compile time, it would give us the best of both worlds (easily maintainable, no overhead during runtime). So, I propose the following (much simplified) scenario. Lets say you wanted to generate a static array (use whatever container suits you best- 2D c array, vector of vectors, etc..) at compile time. You have a function defined- double f(int row, int col); where the return value is the entry in the table, row is the lookup table row, and col is the lookup table column. Is it possible to generate this static array at compile time using templates, and how?

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  • Is "for(;;)" faster than "while (TRUE)"? If not, why do people use it?

    - by Chris Cooper
    for (;;) { //Something to be done repeatedly } I have seen this sort of thing used a lot, but I think it is rather strange... Wouldn't it be much clearer to say while (TRUE), or something along those lines? I'm guessing that (as is the reason for many-a-programmer to resort to cryptic code) this is a tiny margin faster? Why, and is it REALLY worth it? If so, why not just define it this way: #DEFINE while(TRUE) for(;;)

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  • "variable tracking" is eating my compile time!

    - by wowus
    I have an auto-generated file which looks something like this... static void do_SomeFunc1(void* parameter) { // Do stuff. } // Continues on for another 4000 functions... void dispatch(int id, void* parameter) { switch(id) { case ::SomeClass1::id: return do_SomeFunc1(parameter); case ::SomeClass2::id: return do_SomeFunc2(parameter); // This continues for the next 4000 cases... } } When I build it like this, the build time is enormous. If I inline all the functions automagically into their respective cases using my script, the build time is cut in half. GCC 4.5.0 says ~50% of the build time is being taken up by "variable tracking" when I use -ftime-report. What does this mean and how can I speed compilation while still maintaining the superior cache locality of pulling out the functions from the switch? EDIT: Interestingly enough, the build time has exploded only on debug builds, as per the following profiling information of the whole project (which isn't just the file in question, but still a good metric; the file in question takes the most time to build): Debug: 8 minutes 50 seconds Release: 4 minutes, 25 seconds

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  • improving drawing pythagoras tree

    - by sasquatch90
    Hello. I have written program for drawing pythagoras tree fractal. Can anybody see any way of improving it ? Now it is 120 LOc. I was hoping to shorten it to ~100... import javax.swing.*; import java.util.Scanner; import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import javax.swing.JComponent; public class Main extends JFrame {; public Main(int n) { setSize(900, 900); setTitle("Pythagoras tree"); Draw d = new Draw(n); add(d); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setVisible(true); } private int pow(int n){ int pow = 2; for(int i = 1; i < n; i++){ if(n==0){ pow = 1; } pow = pow*2; } return pow; } public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Give amount of steps: "); int steps = sc.nextInt(); new Main(steps); } } class Draw extends JComponent { private int height; private int width; private int steps; public Draw(int n) { height = 800; width = 800; steps = n; Dimension d = new Dimension(width, height); setMinimumSize(d); setPreferredSize(new Dimension(d)); setMaximumSize(d); } @Override public void paintComponent(Graphics g) { super.paintComponent(g); g.setColor(Color.white); g.fillRect(0, 0, width, height); g.setColor(Color.black); int w = width; int h = height; int x1, x2, x3, x4, x5, y1, y2, y3, y4, y5; int base = w/7; x1 = (w/2)-(base/2); x2 = x1; x3 = (w/2)+(base/2); x4 = x3; x5 = w/2; y1 = (h-(h/15))-base; y2 = h-(h/15); y3 = y2; y4 = y1; y5 = (h-(h/15))-(base+(base/2)); //paint g.drawLine(x1, y1, x2, y2); g.drawLine(x2, y2, x3, y3); g.drawLine(x3, y3, x4, y4); g.drawLine(x1, y1, x4, y4); int n1 = steps; n1--; if(n1>0){ g.drawLine(x1, y1, x5, y5); g.drawLine(x4, y4, x5, y5); paintMore(n1, g, x1, x5, x4, y1, y5, y4); paintMore(n1, g, x4, x5, x1, y4, y5, y1); } } public void paintMore(int n1, Graphics g, double x1_1, double x2_1, double x3_1, double y1_1, double y2_1, double y3_1){ double x1, x2, x3, x4, x5, y1, y2, y3, y4, y5; //counting x1 = x1_1 + (x2_1-x3_1); x2 = x1_1; x3 = x2_1; x4 = x2_1 + (x2_1-x3_1); x5 = ((x2_1 + (x2_1-x3_1)) + ((x2_1-x3_1)/2)) + ((x1_1-x2_1)/2); y1 = y1_1 + (y2_1-y3_1); y2 = y1_1; y3 = y2_1; y4 = y2_1 + (y2_1-y3_1); y5 = ((y1_1 + (y2_1-y3_1)) + ((y2_1-y1_1)/2)) + ((y2_1-y3_1)/2); //paint g.setColor(Color.green); g.drawLine((int)x1, (int)y1, (int)x2, (int)y2); g.drawLine((int)x3, (int)y3, (int)x4, (int)y4); g.drawLine((int)x1, (int)y1, (int)x4, (int)y4); n1--; if(n1>0){ g.drawLine((int)x1, (int)y1, (int)x5, (int)y5); g.drawLine((int)x4, (int)y4, (int)x5, (int)y5); paintMore(n1, g, x1, x5, x4, y1, y5, y4); paintMore(n1, g, x4, x5, x1, y4, y5, y1); } } }

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  • Can I make this two LINQ queries into one query only?

    - by Holli
    From a List of builtAgents I need all items with OptimPriority == 1 and only 5 items with OptimPriority == 0. I do this with two seperate queries but I wonder if I could make this with only one query. IEnumerable<Agent> priorityAgents = from pri in builtAgents where pri.OptimPriority == 1 select pri; IEnumerable<Agent> otherAgents = (from oth in builtAgents where oth.OptimPriority == 0 select oth).Take(5);

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  • Optimize slow ranking query

    - by Juan Pablo Califano
    I need to optimize a query for a ranking that is taking forever (the query itself works, but I know it's awful and I've just tried it with a good number of records and it gives a timeout). I'll briefly explain the model. I have 3 tables: player, team and player_team. I have players, that can belong to a team. Obvious as it sounds, players are stored in the player table and teams in team. In my app, each player can switch teams at any time, and a log has to be mantained. However, a player is considered to belong to only one team at a given time. The current team of a player is the last one he's joined. The structure of player and team is not relevant, I think. I have an id column PK in each. In player_team I have: id (PK) player_id (FK -> player.id) team_id (FK -> team.id) Now, each team is assigned a point for each player that has joined. So, now, I want to get a ranking of the first N teams with the biggest number of players. My first idea was to get first the current players from player_team (that is one record top for each player; this record must be the player's current team). I failed to find a simple way to do it (tried GROUP BY player_team.player_id HAVING player_team.id = MAX(player_team.id), but that didn't cut it. I tried a number of querys that didn't work, but managed to get this working. SELECT COUNT(*) AS total, pt.team_id, p.facebook_uid AS owner_uid, t.color FROM player_team pt JOIN player p ON (p.id = pt.player_id) JOIN team t ON (t.id = pt.team_id) WHERE pt.id IN ( SELECT max(J.id) FROM player_team J GROUP BY J.player_id ) GROUP BY pt.team_id ORDER BY total DESC LIMIT 50 As I said, it works but looks very bad and performs worse, so I'm sure there must be a better way to go. Anyone has any ideas for optimizing this? I'm using mysql, by the way. Thanks in advance Adding the explain. (Sorry, not sure how to format it properly) id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t ALL PRIMARY NULL NULL NULL 5000 Using temporary; Using filesort 1 PRIMARY pt ref FKplayer_pt77082,FKplayer_pt265938,new_index FKplayer_pt77082 4 t.id 30 Using where 1 PRIMARY p eq_ref PRIMARY PRIMARY 4 pt.player_id 1 2 DEPENDENT SUBQUERY J index NULL new_index 8 NULL 150000 Using index

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  • AppFabric caching's local cache isnt working for us... What are we doing wrong?

    - by Olly
    We are using appfabric as the 2ndlevel cache for an NHibernate asp.net application comprising a customer facing website and an admin website. They are both connected to the same cache so when admin updates something, the customer facing site is updated. It seems to be working OK - we have a CacheCLuster on a seperate server and all is well but we want to enable localcache to get better performance, however, it dosnt seem to be working. We have enabled it like this... bool UseLocalCache = int LocalCacheObjectCount = int.MaxValue; TimeSpan LocalCacheDefaultTimeout = TimeSpan.FromMinutes(3); DataCacheLocalCacheInvalidationPolicy LocalCacheInvalidationPolicy = DataCacheLocalCacheInvalidationPolicy.TimeoutBased; if (UseLocalCache) { configuration.LocalCacheProperties = new DataCacheLocalCacheProperties( LocalCacheObjectCount, LocalCacheDefaultTimeout, LocalCacheInvalidationPolicy ); // configuration.NotificationProperties = new DataCacheNotificationProperties(500, TimeSpan.FromSeconds(300)); } Initially we tried using a timeout invalidation policy (3mins) and our app felt like it was running faster. HOWEVER, we noticed that if we changed something in the admin site, it was immediatley updated in the live site. As we are using timeouts not notifications, this demonstrates that the local cache isnt being queried (or is, but is always missing). The cache.GetType().Name returns "LocalCache" - so the factory has made a local cache. Running "Get-Cache-Statistics MyCache" in PS on my dev environment (asp.net app running local from vs2008, cache cluster running on a seperate w2k8 machine) show a handful of Request Counts. However, on the Production environment, the Request Count increases dramaticaly. We tried following the method here to se the cache cliebt-server traffic... http://blogs.msdn.com/b/appfabriccat/archive/2010/09/20/appfabric-cache-peeking-into-client-amp-server-wcf-communication.aspx but the log file had nothing but the initial header in it - i.e no loggin either. I cant find anything in SO or Google. Have we done something wrong? Have we got a screwy install of AppFabric - we installed it via WebPlatform Installer - I think? (note: the IIS box running ASp.net isnt in yhe cluster - it is just the client). Any insights greatfully received!

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  • Optimize master-detail insert statements

    - by Dave Jarvis
    Quest After a day of running (against nearly 1 GB of data), a set of statements are tumbling down to 40 inserts per second. I am looking to increase that by an order of magnitude or two. SQL Code The code to insert the information comes in two parts: a master record and detail records. The master record: INSERT INTO MONTH_REF (DISTRICT_ID, STATION_ID, CATEGORY_ID, YEAR, MONTH) VALUES ('101', '0066', '010', 1984, 07); The detail records: INSERT INTO DAILY (MONTH_REF_ID, AMOUNT, DAILY_FLAG_ID, DAY) VALUES ((SELECT ID FROM MONTH_REF M WHERE M.DISTRICT_ID = '101' AND M.STATION_ID = '0066' AND M.CAT EGORY_ID = '010' AND M.YEAR = 1984 AND M.MONTH = 07), 0, ' ', 1); INSERT INTO DAILY (MONTH_REF_ID, AMOUNT, DAILY_FLAG_ID, DAY) VALUES ((SELECT ID FROM MONTH_REF M WHERE M.DISTRICT_ID = '101' AND M.STATION_ID = '0066' AND M.CAT EGORY_ID = '010' AND M.YEAR = 1984 AND M.MONTH = 07), 0.5, ' ', 2); INSERT INTO DAILY (MONTH_REF_ID, AMOUNT, DAILY_FLAG_ID, DAY) VALUES ((SELECT ID FROM MONTH_REF M WHERE M.DISTRICT_ID = '101' AND M.STATION_ID = '0066' AND M.CAT EGORY_ID = '010' AND M.YEAR = 1984 AND M.MONTH = 07), 0, 'T', 3); Proposed Solution INSERT INTO MONTH_REF (DISTRICT_ID, STATION_ID, CATEGORY_ID, YEAR, MONTH) VALUES ('101', '0066', '010', 1984, 07); SET @month_ref_id := (SELECT LAST_INSERT_ID()); INSERT INTO DAILY (MONTH_REF_ID, AMOUNT, DAILY_FLAG_ID, DAY) VALUES (@month_ref_id, 0, ' ', 1); INSERT INTO DAILY (MONTH_REF_ID, AMOUNT, DAILY_FLAG_ID, DAY) VALUES (@month_ref_id, 0.5, ' ', 2); INSERT INTO DAILY (MONTH_REF_ID, AMOUNT, DAILY_FLAG_ID, DAY) VALUES (@month_ref_id, 0, 'T', 3); Constraints The MONTH_REF table has an AUTO_INCREMENT primary key and is indexed on it. The DAILY table has no index and no primary key. A primary key can be added to the DAILY table, if it would help. Question Is there a more efficient way to execute the (billion or so) insert statements than the proposed solution? Thank you!

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  • Biggest performance improvement you've had with the smallest change?

    - by JoelFan
    What's the biggest performance improvement you've had with the smallest change? For example, I once improved the performance of a certain page on a high-profile web app by a factor of 10, just by moving "where customerID = ?" to a different place inside a complicated SQL statement (before my change it had been selecting all customers in a join, then later selecting out the desired customer).

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