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  • Auto DOP and Concurrency

    - by jean-pierre.dijcks
    After spending some time in the cloud, I figured it is time to come down to earth and start discussing some of the new Auto DOP features some more. As Database Machines (the v2 machine runs Oracle Database 11.2) are effectively selling like hotcakes, it makes some sense to talk about the new parallel features in more detail. For basic understanding make sure you have read the initial post. The focus there is on Auto DOP and queuing, which is to some extend the focus here. But now I want to discuss the concurrency a little and explain some of the relevant parameters and their impact, specifically in a situation with concurrency on the system. The goal of Auto DOP The idea behind calculating the Automatic Degree of Parallelism is to find the highest possible DOP (ideal DOP) that still scales. In other words, if we were to increase the DOP even more  above a certain DOP we would see a tailing off of the performance curve and the resource cost / performance would become less optimal. Therefore the ideal DOP is the best resource/performance point for that statement. The goal of Queuing On a normal production system we should see statements running concurrently. On a Database Machine we typically see high concurrency rates, so we need to find a way to deal with both high DOP’s and high concurrency. Queuing is intended to make sure we Don’t throttle down a DOP because other statements are running on the system Stay within the physical limits of a system’s processing power Instead of making statements go at a lower DOP we queue them to make sure they will get all the resources they want to run efficiently without trashing the system. The theory – and hopefully – practice is that by giving a statement the optimal DOP the sum of all statements runs faster with queuing than without queuing. Increasing the Number of Potential Parallel Statements To determine how many statements we will consider running in parallel a single parameter should be looked at. That parameter is called PARALLEL_MIN_TIME_THRESHOLD. The default value is set to 10 seconds. So far there is nothing new here…, but do realize that anything serial (e.g. that stays under the threshold) goes straight into processing as is not considered in the rest of this post. Now, if you have a system where you have two groups of queries, serial short running and potentially parallel long running ones, you may want to worry only about the long running ones with this parallel statement threshold. As an example, lets assume the short running stuff runs on average between 1 and 15 seconds in serial (and the business is quite happy with that). The long running stuff is in the realm of 1 – 5 minutes. It might be a good choice to set the threshold to somewhere north of 30 seconds. That way the short running queries all run serial as they do today (if it ain’t broken, don’t fix it) and allows the long running ones to be evaluated for (higher degrees of) parallelism. This makes sense because the longer running ones are (at least in theory) more interesting to unleash a parallel processing model on and the benefits of running these in parallel are much more significant (again, that is mostly the case). Setting a Maximum DOP for a Statement Now that you know how to control how many of your statements are considered to run in parallel, lets talk about the specific degree of any given statement that will be evaluated. As the initial post describes this is controlled by PARALLEL_DEGREE_LIMIT. This parameter controls the degree on the entire cluster and by default it is CPU (meaning it equals Default DOP). For the sake of an example, let’s say our Default DOP is 32. Looking at our 5 minute queries from the previous paragraph, the limit to 32 means that none of the statements that are evaluated for Auto DOP ever runs at more than DOP of 32. Concurrently Running a High DOP A basic assumption about running high DOP statements at high concurrency is that you at some point in time (and this is true on any parallel processing platform!) will run into a resource limitation. And yes, you can then buy more hardware (e.g. expand the Database Machine in Oracle’s case), but that is not the point of this post… The goal is to find a balance between the highest possible DOP for each statement and the number of statements running concurrently, but with an emphasis on running each statement at that highest efficiency DOP. The PARALLEL_SERVER_TARGET parameter is the all important concurrency slider here. Setting this parameter to a higher number means more statements get to run at their maximum parallel degree before queuing kicks in.  PARALLEL_SERVER_TARGET is set per instance (so needs to be set to the same value on all 8 nodes in a full rack Database Machine). Just as a side note, this parameter is set in processes, not in DOP, which equates to 4* Default DOP (2 processes for a DOP, default value is 2 * Default DOP, hence a default of 4 * Default DOP). Let’s say we have PARALLEL_SERVER_TARGET set to 128. With our limit set to 32 (the default) we are able to run 4 statements concurrently at the highest DOP possible on this system before we start queuing. If these 4 statements are running, any next statement will be queued. To run a system at high concurrency the PARALLEL_SERVER_TARGET should be raised from its default to be much closer (start with 60% or so) to PARALLEL_MAX_SERVERS. By using both PARALLEL_SERVER_TARGET and PARALLEL_DEGREE_LIMIT you can control easily how many statements run concurrently at good DOPs without excessive queuing. Because each workload is a little different, it makes sense to plan ahead and look at these parameters and set these based on your requirements.

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  • How to test using conditional defines if the application is Firemonkey one?

    - by Gad D Lord
    I use DUnit. It has an VCL GUITestRunner and a console TextTestRunner. In an unit used by both Firemonkey and VCL Forms applications I would like to achieve the following: If Firemonkey app, if target is OS X, and executing on OS X - TextTestRunner If Firemonkey app, if target is 32-bit Windows, executing on Windows - AllocConsole + TextTestRunner If VCL app - GUITestRunner {$IFDEF MACOS} TextTestRunner.RunRegisteredTests; // Case 1 {$ELSE} {$IFDEF MSWINDOWS} AllocConsole; {$ENDIF} {$IFDEF FIREMONKEY_APP} // Case 2 <--------------- HERE TextTestRunner.RunRegisteredTests; {$ELSE} // Case 3 GUITestRunner.RunRegisteredTests; {$IFEND} {$ENDIF} Which is the best way to make Case 2 work?

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  • Java Prepared Statement Error

    - by Suresh S
    Hi Guys the following code throws me an error i have an insert statement created once and in the while loop i am dynamically setting parameter , and at the end i says ps2.addBatch() again while ( (eachLine = in.readLine()) != null)) { for (int k=stat; k <=45;k++) { ps2.setString (k,main[(k-2)]); } stat=45; for (int l=1;l<= 2; l++) { ps2.setString((stat+l),pdp[(l-1)]);// Exception } ps2.addBatch(); } This is the error java.lang.ArrayIndexOutOfBoundsException: 45 at oracle.jdbc.dbaccess.DBDataSetImpl._getDBItem(DBDataSetImpl.java:378) at oracle.jdbc.dbaccess.DBDataSetImpl._createOrGetDBItem(DBDataSetImpl.java:781) at oracle.jdbc.dbaccess.DBDataSetImpl.setBytesBindItem(DBDataSetImpl.java:2450) at oracle.jdbc.driver.OraclePreparedStatement.setItem(OraclePreparedStatement.java:1155) at oracle.jdbc.driver.OraclePreparedStatement.setString(OraclePreparedStatement.java:1572) at Processor.main(Processor.java:233)

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  • Most readable way to write simple conditional check

    - by JRL
    What would be the most readable/best way to write a multiple conditional check such as shown below? Two possibilities that I could think of (this is Java but the language really doesn't matter here): Option 1: boolean c1 = passwordField.getPassword().length > 0; boolean c2 = !stationIDTextField.getText().trim().isEmpty(); boolean c3 = !userNameTextField.getText().trim().isEmpty(); if (c1 && c2 && c3) { okButton.setEnabled(true); } Option 2: if (passwordField.getPassword().length > 0 && !stationIDTextField.getText().trim().isEmpty() && !userNameTextField.getText().trim().isEmpty() { okButton.setEnabled(true); } What I don't like about option 2 is that the line wraps and then indentation becomes a pain. What I don't like about option 1 is that it creates variables for nothing and requires looking at two places. So what do you think? Any other options?

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  • How to understand "if ( obj.length === +obj.length )" Javascript condition statement?

    - by humanityANDpeace
    I have run across a condition statement which I have some difficulties to understand. It looks like (please note the +-sign on the right-hand-side) this: obj.length === +obj.length. Can this condition and its purpose/syntax be explained? Looking at the statement (without knowing it) provokes the impression that it is a dirty hack of some sort, but I am almost certain that underscore.js is rather a well designed library, so there must be a better explanation. Background I found this statement used in some functions of the underscore.js library (underscore.js annotated source). My guesswork is that this condition statement is somehow related to testing for a variable obj to be of Array type? (but I am totally unsure). I have tried to test this using this code. var myArray = [1,2,3]; testResult1 = myArray.length === +myArray.length; console.log( testResult1 ); //prints true var myObject = { foo : "somestring", bar : 123 }; testResult2 = myObject.length === +myObject.length; console.log( testResult2 ); //prints false

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  • Return cell reference as result of if statement with vlookups.

    - by EMJ
    I have two sets of data in excel. One contains a set of data which represents the initial step of a process. The other set of data represents the additional steps which take place after the first step is completed. Each of the data records in the "additional step data" has an id in a column. I need to find the identifying codes of the "additional step data" which correspond with the initial step data records. The problem is that I have to match the data in 4 columns between the two data sets and return the id of the "additional step data". I started by doing a combination of an if and vlookup functions, but I got stuck when I tried to figure out how to get the if statement to reference the id of the matching "additional step data". Basically I am trying to avoid having to search by manually filtering between two sets of data and finding corresponding records. Does anyone have any idea about how to do this?

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  • Rails - Create if record doesn't exist or else update.....Whats Best way to do this?

    - by ChrisWesAllen
    Hi, I have a create statement for some models but its creating a record within a join table regardless if the record exist. Here is what my code looks like. @user = User.find(current_user) @event = Event.find(params[:id]) for interest in @event.interests @user.choices.create(:interest => interest, :score => 4) end The problem is it creates records no matter what. I would like it to create a record if it doesnt exist, if a record does exist I would just to it to take the attribute of the found record and add or subtract 1. So, I've been looking around and I see something called find_or_create_by. My question is what happens if it finds? Preferably if it finds,I would like to take the current :score attribute and +1. SO is it possible to find or create by id? I'm not sure what attribute I would find by since the model I'm looking at is a join model which only had id foreign keys and the score attribute. I tried @user.choices.find_or_create_by_user(:user => @user.id, :interest => interest, :score => 4) but got "undefined method `find_by_user'".....ANy ideas or help?

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  • The Cash or Credit problem

    - by Josh K
    If you go to a store and ask "Cash or Credit?" they might simply say "Yes." This doesn't tell you anything as you posed an OR statement. if(cash || credit) With humans it's possible that they might respond "Both" to that question, or "Only {cash | credit}." Is there a way (or operator) to force the a statement to return the TRUE portions of a statement? For example: boolean cash = true; boolean credit = true; boolean cheque = false; if(cash || credit || cheque ) { // In here you would have an array with cash and credit in it because both of those are true }

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  • switch vs. if...else if...else

    - by John Hartsock
    Guys I have a couple of questions: Is there a preformance difference in Javascript between a switch statement and an if...else if....else? If so why? Is the behavior of switch and if...else if...else different across browsers? (FireFox, IE, Chrome, Opera, Safari) The reason for asking this question is it seems that I get better preformance on a switch statement with approx 100 cases in Firefox. But in IE it get better preformance with 100 if...else if...else.

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  • EXPORT AS INSERT STATEMENTS: But in SQL Plus the line overrides 2500 characters!

    - by The chicken in the kitchen
    Hello, I have to export an Oracle table as INSERT STATEMENTS. But the INSERT STATEMENTS so generated, override 2500 characters. I am obliged to execute them in SQL Plus, so I receive an error message. This is my Oracle table: CREATE TABLE SAMPLE_TABLE ( C01 VARCHAR2 (5 BYTE) NOT NULL, C02 NUMBER (10) NOT NULL, C03 NUMBER (5) NOT NULL, C04 NUMBER (5) NOT NULL, C05 VARCHAR2 (20 BYTE) NOT NULL, c06 VARCHAR2 (200 BYTE) NOT NULL, c07 VARCHAR2 (200 BYTE) NOT NULL, c08 NUMBER (5) NOT NULL, c09 NUMBER (10) NOT NULL, c10 VARCHAR2 (80 BYTE), c11 VARCHAR2 (200 BYTE), c12 VARCHAR2 (200 BYTE), c13 VARCHAR2 (4000 BYTE), c14 VARCHAR2 (1 BYTE) DEFAULT 'N' NOT NULL, c15 CHAR (1 BYTE), c16 CHAR (1 BYTE) ); ASSUMPTIONS: a) I am OBLIGED to export table data as INSERT STATEMENTS; I am allowed to use UPDATE statements, in order to avoid the SQL*Plus error "sp2-0027 input is too long(2499 characters)"; b) I am OBLIGED to use SQL*Plus to execute the script so generated. c) Please assume that every record can contain special characters: CHR(10), CHR(13), and so on; d) I CAN'T use SQL Loader; e) I CAN'T export and then import the table: I can only add the "delta" using INSERT / UPDATE statements through SQL Plus.

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  • In Applescript, why do local variables in handlers capture "with" labeled parameters?

    - by outis
    In Applescript, if you declare a handler using "with" labeled parameters, local variables get the values of the arguments and the parameters themselves are undefined. For example: on bam of thing with frst and scnd local eat_frst return {thing: thing, frst:frst, scnd:scnd} -- this line throws an error end bam bam of "bug-AWWK!" with frst without scnd results in an error message that "scnd" isn't defined in the second line of bam. thing and frst are both defined, getting the arguments passed in the call to bam. Why is this happening? Why is scnd undefined? Note: I know that declaring variables as "local" within a handler is unnecessary. It's done in the examples for illustrative purposes.

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  • Scripting custom drawing in Delphi application with IF/THEN/ELSE statements?

    - by Jerry Dodge
    I'm building a Delphi application which displays a blueprint of a building, including doors, windows, wiring, lighting, outlets, switches, etc. I have implemented a very lightweight script of my own to call drawing commands to the canvas, which is loaded from a database. For example, one command is ELP 1110,1110,1290,1290,3,8388608 which draws an ellipse, parameters are 1110x1110 to 1290x1290 with pen width of 3 and the color 8388608 converted from an integer to a TColor. What I'm now doing is implementing objects with common drawing routines, and I'd like to use my scripting engine, but this calls for IF/THEN/ELSE statements and such. For example, when I'm drawing a light, if the light is turned on, I'd like to draw it yellow, but if it's off, I'd like to draw it gray. My current scripting engine has no recognition of such statements. It just accepts simple drawing commands which correspond with TCanvas methods. Here's the procedure I've developed (incomplete) for executing a drawing command on a canvas: function DrawCommand(const Cmd: String; var Canvas: TCanvas): Boolean; type TSingleArray = array of Single; var Br: TBrush; Pn: TPen; X: Integer; P: Integer; L: String; Inst: String; T: String; Nums: TSingleArray; begin Result:= False; Br:= Canvas.Brush; Pn:= Canvas.Pen; if Assigned(Canvas) then begin if Length(Cmd) > 5 then begin L:= UpperCase(Cmd); if Pos(' ', L)> 0 then begin Inst:= Copy(L, 1, Pos(' ', L) - 1); Delete(L, 1, Pos(' ', L)); L:= L + ','; SetLength(Nums, 0); X:= 0; while Pos(',', L) > 0 do begin P:= Pos(',', L); T:= Copy(L, 1, P - 1); Delete(L, 1, P); SetLength(Nums, X + 1); Nums[X]:= StrToFloatDef(T, 0); Inc(X); end; Br.Style:= bsClear; Pn.Style:= psSolid; Pn.Color:= clBlack; if Inst = 'LIN' then begin Pn.Width:= Trunc(Nums[4]); if Length(Nums) > 5 then begin Br.Style:= bsSolid; Br.Color:= Trunc(Nums[5]); end; Canvas.MoveTo(Trunc(Nums[0]), Trunc(Nums[1])); Canvas.LineTo(Trunc(Nums[2]), Trunc(Nums[3])); Result:= True; end else if Inst = 'ELP' then begin Pn.Width:= Trunc(Nums[4]); if Length(Nums) > 5 then begin Br.Style:= bsSolid; Br.Color:= Trunc(Nums[5]); end; Canvas.Ellipse(Trunc(Nums[0]),Trunc(Nums[1]),Trunc(Nums[2]),Trunc(Nums[3])); Result:= True; end else if Inst = 'ARC' then begin Pn.Width:= Trunc(Nums[8]); Canvas.Arc(Trunc(Nums[0]),Trunc(Nums[1]),Trunc(Nums[2]),Trunc(Nums[3]), Trunc(Nums[4]),Trunc(Nums[5]),Trunc(Nums[6]),Trunc(Nums[7])); Result:= True; end else if Inst = 'TXT' then begin Canvas.Font.Size:= Trunc(Nums[2]); Br.Style:= bsClear; Pn.Style:= psSolid; T:= Cmd; Delete(T, 1, Pos(' ', T)); Delete(T, 1, Pos(',', T)); Delete(T, 1, Pos(',', T)); Delete(T, 1, Pos(',', T)); Canvas.TextOut(Trunc(Nums[0]), Trunc(Nums[1]), T); Result:= True; end; end else begin //No space found, not a valid command end; end; end; end; What I'd like to know is what's a good lightweight third-party scripting engine I could use to accomplish this? I would hate to implement parsing of IF, THEN, ELSE, END, IFELSE, IFEND, and all those necessary commands. I need simply the ability to tell the scripting engine if certain properties meet certain conditions, it needs to draw the object a certain way. The light example above is only one scenario, but the same solution needs to also be applicable to other scenarios, such as a door being open or closed, locked or unlocked, and draw it a different way accordingly. This needs to be implemented in the object script drawing level. I can't hard-code any of these scripting/drawing rules, the drawing needs to be controlled based on the current state of the object, and I may also wish to draw a light a certain shade or darkness depending on how dimmed the light is.

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  • How do you manage Labeled and All-Mail unread mails in Thunderbird with a GMail IMAP accounnt?

    - by Edward Beach
    I use Thunderbird with gmail via imap and do so with multiple accounts. On the gmail side I have filters that will automatically assign labels to incoming mail and archive it moving it out of the inbox. On the Thunderbird side it will see the new mail appear in the corresponding folder and the all mail folder -- that's fine but my problem is that they're both marked as unread. Since I have many accounts I use the unread mail view in Thunderbird's folder panel and what I see is both folders highlighted as unread. When I read the message in one folder the other only get marked as read I click on it and Thunderbird does another imap transaction. Is there a configuration that will recognize the same mail in two different folders automatically?

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  • How should I refactor switch statements like this (Switching on type) to be more OO?

    - by Taytay
    I'm seeing some code like this in our code base, and want to refactor it: (Typescript psuedocode follows): class EntityManager{ private findEntityForServerObject(entityType:string, serverObject:any):IEntity { var existingEntity:IEntity = null; switch(entityType) { case Types.UserSetting: existingEntity = this.getUserSettingByUserIdAndSettingName(serverObject.user_id, serverObject.setting_name); break; case Types.Bar: existingEntity = this.getBarByUserIdAndId(serverObject.user_id, serverObject.id); break; //Lots more case statements here... } return existingEntity; } } The downsides of switching on type are self-explanatory. Normally, when switching behavior based on type, I try to push the behavior into subclasses so that I can reduce this to a single method call, and let polymorphism take care of the rest. However, the following two things are giving me pause: 1) I don't want to couple the serverObject with the class that is storing all of these objects. It doesn't know where to look for entities of a certain type. And unfortunately, the identity of a type of ServerObject varies with the type of ServerObject. (So sometimes it's just an ID, other times it's a combination of an id and a uniquely identifying string, etc). And this behavior doesn't belong down there on those subclasses. It is the responsibility of the EntityManager and its delegates. 2) In this case, I can't modify the ServerObject classes since they're plain old data objects. It should be mentioned that I've got other instances of the above method that take a parameter like "IEntity" and proceed to do almost the same thing (but slightly modify the name of the methods they're calling to get the identity of the entity). So, we might have: case Types.Bar: existingEntity = this.getBarByUserIdAndId(entity.getUserId(), entity.getId()); break; So in that case, I can change the entity interface and subclasses, but this isn't behavior that belongs in that class. So, I think that points me to some sort of map. So eventually I will call: private findEntityForServerObject(entityType:string, serverObject:any):IEntity { return aMapOfSomeSort[entityType].findByServerObject(serverObject); } private findEntityForEntity(someEntity:IEntity):IEntity { return aMapOfSomeSort[someEntity.entityType].findByEntity(someEntity); } Which means I need to register some sort of strategy classes/functions at runtime with this map. And again, I darn well better remember to register one for each my my types, or I'll get a runtime exception. Is there a better way to refactor this? I feel like I'm missing something really obvious here.

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  • can I see all SQL statements sent over an ODBC connection?

    - by Dave Cameron
    I'm working with a third-party application that uses ODBC to connect to, and alter, a database. During certain failure modes, the end-results are not what I expect. To understand it better, I'd like some way of inspecting all the statements sent to the database. Is there a way to do this with ODBC? I know with JDBC I could use http://www.p6spy.com/ to see all statements sent, for example when debugging hibernate. p6spy is a "proxy" driver that records commands sent and forwards them on to the real JDBC driver. Another possibility might be a protocol sniffer that would capture statements over the wire. Although, I'm unsure if ODBC includes a standard wire protocol, or only specifieds the API. Does anyone know of existing tools that would allow me to do either of these things? Alternatively, is there another approach I could take?

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  • How to leave out some statements while executing java code?

    - by iamrohitbanga
    In C++ if we do not want some statements to compile into code that ships like assert function calls, we control their compilation through #ifndef preprocessor directives. How do we do this in Java? I have some System.out.println() statements for debugging which I would like to remove for the final code. one way is to make them execute conditionally under the affect of a boolean variable. Is there a better way of doing this? As I have a java swing application I can turn off the System.out.println statements without affecting the output. What is the method of doing this?

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  • Is there a way to customise messages produced by statements in MS SQL Query Analyzer?

    - by Scott Leis
    If I run a simple query in SQL Query Analyzer, like: SELECT * FROM TableName the Messages pane always produces a message like: (30 row(s) affected) If I run a stored procedure with many statements, the messages are useless because there's no indication of what each one relates to. So firstly: Is there a way to customise the default messages on a per-query basis? E.g. I'd like a specific query to produce a message like: TableName query produced [numRowsAffected] results. replacing [numRowsAffected] with the number that would have appeared in the default message. Secondly, is there a way to suppress the default messages on a per-query basis? E.g. I have a local variable of type TABLE, used in several statements. I don't want any message to appear for statements where I'm just deleting data from that variable before re-using it. I'm seeking solutions that work in SQL Server 8.0.

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  • How to leave out some System.out/logging statements while executing java code?

    - by iamrohitbanga
    In C++ if we do not want some statements to compile into code that ships like assert function calls, we control their compilation through #ifndef preprocessor directives. How do we do this in Java? I have some System.out.println() statements for debugging which I would like to remove for the final code. one way is to make them execute conditionally under the affect of a boolean variable. Is there a better way of doing this? As I have a java swing application I can turn off the System.out.println statements without affecting the output. What is the method of doing this?

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  • After writing SQL statements in MySQL, how to measure the speed / performance of them?

    - by Jian Lin
    I saw something from an "execution plan" article: 10 rows fetched in 0.0003s (0.7344s) How come there are 2 durations shown? What if I don't have large data set yet. For example, if I have only 20, 50, or even just 100 records, I can't really measure how faster 2 different SQL statements compare in term of speed in real life situation? In other words, there needs to be at least hundreds of thousands of records, or even a million records to accurately compares the performance of 2 different SQL statements?

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