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SQL Server - Query Short-Circuiting?

- by Sam Schutte

Do T-SQL queries in SQL Server support short-circuiting? For instance, I have a situation where I have two database and I'm comparing data between the two tables to match and copy some info across. In one table, the "ID" field will always have leading zeros (such as "000000001234"), and in the other table, the ID field may or may not have leading zeros (might be "000000001234" or "1234"). So my query to match the two is something like: select * from table1 where table1.ID LIKE '%1234' To speed things up, I'm thinking of adding an OR before the like that just says: table1.ID = table2.ID to handle the case where both ID's have the padded zeros and are equal. Will doing so speed up the query by matching items on the "=" and not evaluating the LIKE for every single row (will it short circuit and skip the LIKE)?

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General rule - when to use a model (Codeigniter)

- by pingu

Hi guys, I was just curious as to what the rule of thumb was for models. Generally, I use them only for situations where I need to add/edit or update database entries for an object. However, I'm building an app at the moment that has a "config" table which holds various data, such as last updated, which will control when certain features in the app should be displayed. In this instance, I will mostly need to retrieve data from the config table. Is it worth putting these config methods in model? I'm interested to hear how more experienced coders approach the MVC methodology in CI - example pseudo methods (e.g., what methods relating to the same object you'd use in the model and the controller) would be most helpful.

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Counting multiple entries in a MySQL database?

- by Aaron

Hi all, I'm trying to count multiple entries in a MySQL database, I know how to use COUNT(), but the exact syntax I want to get the results I need eludes me. The problem: Table structure: ID, CODE, AUTHOR, COUNTRY, TIMESTAMP. Code, Author and Country overlap many times in the table. I am trying to discover if there is one simple query that can be ran to return (using WHERE clause on COUNTRY) the author field, the code field, and then a final field that counts the number of times the CODE was present in the query result. So, theoretically I could end up with an array like: array('author', 'code', 'codeAppearsNTimes'); Authors also have varying codes associated with them, so I don't want the results merged. I suppose the end result would be: 'This author is associated with this code this many times'. Is this possible with MySQL? Thanks in advance.

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HQL query for entity with max value

- by Rob

I have a Hibernate entity that looks like this (accessors ommitted for brevity): @Entity @Table(name="FeatureList_Version") @SecondaryTable(name="FeatureList", pkJoinColumns=@PrimaryKeyJoinColumn(name="FeatureList_Key")) public class FeatureList implements Serializable { @Id @Column(name="FeatureList_Version_Key") private String key; @Column(name="Name",table="FeatureList") private String name; @Column(name="VERSION") private Integer version; } I want to craft an HQL query that retrieves the most up to date version of a FeatureList. The following query sort of works: Select f.name, max(f.version) from FeatureList f group by f.name The trouble is that won't populate the key field, which I need to contain the key of the record with the highest version number for the given FeatureList. If I add f.key in the select it won't work because it's not in the group by or an aggregate and if I put it in the group by the whole thing stops working and it just gives me every version as a separate entity. So, can anybody help?

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Two different tables or just one with bool column?

- by Aidas

We have two tables: OriginalDocument and ProcessedDocument. In the first one we put an original, not processed document. After it's validated and processed (converted to our xml format and parsed), it's put into Document table. Processed document can be valid or invalid. Which makes more sense: have two different tables for valid and invalid documents or just have one with 'Valid' column? Some of the columns (~5-7) are irrelevant for invalid document. Storing both invalid and valid documents would also make Document table filled with 'NULL' columns (if document is invalid, information like document number, receiver can be unknown). What else should we consider and weigh, when making this decision?

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operating systems - TLBs

- by stabGreeol

I'm trying to get my head round this (okay, tbh cramming a night before the exams :) but i can't figure out (nor find a good high level overview on the net) of this: 'page table entries can be mapped to more than one TLB entry.. if for example every page table entry is mappped to two TLB entries, this is know as 2-way set associative TLB' My question is, why would we want to map this more than once? surely we want to have the maximum number of possible entries represented in the TLB, and duplication would waste space right ? What am i missing? Many thanks

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sql query to get the sql server 2005

- by subash

i have table with filmname and actors column in sql server 2005 i want the sql query to get all the actors of the film starred by both "bradpitt" and "rusellcrowe"

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How to make a sum of total for each id

- by JetJack

Using Crystal report 7 I want to view the table 1 and sum of table2 table1 id name 001 raja 002 vijay 003 suresh .... table2 id value 001 100 001 200 001 150 002 200 003 150 003 200 ... I want to display all the rows from table1 and sum(values) from table2. How to do this in crystal report Expected Output id name value 001 raja 450 002 vijay 200 003 suresh 350 .... Note: I add the table field directly to the report, i am not added store procedure or views or query in the report. How to do this. Need Crystal report help

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Query to find all the nodes that are two steps away from a particular node.

- by iecut

Suppose I have two columns in a table that represents a graph, the first column is a FROMNODE and second one is TONODE. What I would like to know is that how will we find all the nodes that are two steps away from a particular node. Lets suppose I have a node numbered '1' and i would like to know all the nodes that are two steps away from it. I have tried(I am assuming the table name as graph) SELECT FROMNODE FROM GRAPH WHERE TONODE=1 (this is to select all the nodes that are connected to node 1, but I couldn't figure out how would I find all the nodes that are two steps away from node 1??)

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How do I find hash value of a 3D vector ?

- by brainydexter

I am trying to perform broad-phase collision detection with a fixed-grid size approach. Thus, for each entity's position: (x,y,z) (each of type float), I need to find which cell does the entity lie in. I then intend to store all the cells in a hash-table and then iterate through to report (if any) collisions. So, here is what I am doing: Grid-cell's position: (int type) (Gx, Gy, Gz) = (x / M, y / M, z / M) where M is the size of the grid. Once, I have a cell, I'd like to add it to a hash-table with its key being a unique hash based on (Gx, Gy, Gz) and the value being the cell itself. Now, I cannot think of a good hash function and I need some help with that. Can someone please suggest me a good hash function? Thanks

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Repeating fields in similar database tables

- by user1738833

I have been tasked with working on a database that I have never seen before and I'm looking at the DB structure. Some of the central and most heavily queried and joined tables look like virtual duplicates of each other. Here's a massively simplified representation of the situation, with business-sensitive information changed, listing hypothetical table names and fields: TopLevelGroup: PK_TLGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK SubGroup: PK_SubGroupId, FK_ParentTopLevelGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK SubSubGroup: PK_SubSUbGroupId, FK_ParentSubGroupId, DisplaysXOnBill, DisplaysYOnBill, IsInvoicedForJ, IsInvoicedForK I haven't listed the types of the fields as I don't think it's particularly important to the situation. In addition, it's worth saying that rather than four repeated fields as in the example above, I'm looking at 86 repeated fields. For the most part, those fields genuinely do represent "facts" about the primary table entity, so it's not automatically wrong for that reason. In addition, the "groups" represented here have a property inheritance relationship. If DisplaysXOnBill is NULL in the SubSubGroup, it takes the value of DisplaysXOnBillfrom it's parent, the SubGroup, and so-on up to the TopLevelGroup. Further, the requirements will never require that the model extends beyond three levels, so there is no need for flexibility in that area. Is there a design smell from several tables which describe very similar entities having almost identical fields? If so, what might be a better design of the example above? I'm using the phrase "design smell" to indicate a possible problem. Of course, in any given situation, a particular design might well be the best solution. I'm looking for a more general answer - wondering what might be wrong with this design and what might be the better design were that the case. Possibly related, but not primary questions: Is this database schema in a reasonably normal form (e.g. to 3NF), insofar as can be told from the information I've provided. I can't see a problem with the requirements of 2NF and 3NF, except in their inheriting the requirements of 1NF. Is 1NF satisfied though? Are repeating groups allowed in different tables? Is there a best-practice method for implementing the inheritance relationship in a database as I require? The method above feels clunky to me because any query on the SubSubGroup necessarily needs to join onto the SubGroup and the TopLevelGroup tables to collect inherited facts, which can make even trivial joins requiring facts from the SubSubGroup table rather long-winded. There are, of course, political considerations to making a relatively large change like this. For the purpose of this question, I'm happy to ignore that fact in the interests of keeping the answers ring-fenced to the technical problem.

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deselectRowAtIndexPath on an ABPeoplePickerNavigationController

- by Josh Wright

I'm showing an ABPeoplePickerNavigationController as a tab in my app. The user clicks a name, then email address, then I do something with the email address. Afterwards, I'd like for the person and property that they selected to fade out (not be highlighted). In a normal table, I'd call deselectRowAtIndexPath. But with the ABPeoplePickerNavCont I don't seem to have access to it's table, nor do I know what indexPath is selected, nor is there an api for deselecting the row. On most apps, ABPeoplePickerNavCont is used modally so it doesn't matter that the row is still highlighted 'cause the whole thing gets dismissed. But in my app it does not get dismissed (just like the contacts tab in the Phone app). Any ideas?

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dump csv from sqlalchemy

- by afilatun

For some reason, I want to dump a table from a database (sqlite3) in the form of a csv file. I'm using a python script with elixir (based on sqlalchemy) to modify the database. I was wondering if there is any way to dump the table I use to csv. I've seen sqlalchemy serializer but it doesn't seem to be what I want. Am I doing it wrong? Should I call the sqlite3 python module after closing my sqlalchemy session to dump to a file instead? Or should I use something homemade?

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ODEE Green Field (Windows) Part 4 - Documaker

- by AndyL-Oracle

Welcome back! We're about nearing completion of our installation of Oracle Documaker Enterprise Edition ("ODEE") in a green field. In my previous post, I covered the installation of SOA Suite for WebLogic. Before that, I covered the installation of WebLogic, and Oracle 11g database - all of which constitute the prerequisites for installing ODEE. Naturally, if your environment already has a WebLogic server and Oracle database, then you can skip all those components and go straight for the heart of the installation of ODEE. The ODEE installation is comprised of two procedures, the first covers the installation, which is running the installer and answering some questions. This will lay down the files necessary to install into the tiers (e.g. database schemas, WebLogic domains, etcetera). The second procedure is to deploy the configuration files into the various components (e.g. deploy the database schemas, WebLogic domains, SOA composites, etcetera). I will segment my posts accordingly! Let's get started, shall we? Unpack the installation files into a temporary directory location. This should extract a zip file. Extract that zip file into the temporary directory location. Navigate to and execute the installer in Disk1/setup.exe. You may have to allow the program to run if User Account Control is enabled. Once the dialog below is displayed, click Next. Select your ODEE Home - inside this directory is where all the files will be deployed. For ease of support, I recommend using the default, however you can put this wherever you want. Click Next. Select the database type, database connection type – note that the database name should match the value used for the connection type (e.g. if using SID, then the name should be IDMAKER; if using ServiceName, the name should be “idmaker.us.oracle.com”). Verify whether or not you want to enable advanced compression. Note: if you are not licensed for Oracle 11g Advanced Compression option do not use this option! Terrible, terrible calamities will befall you if you do! Click Next. Enter the Documaker Admin user name (default "dmkr_admin" is recommended for support purposes) and set the password. Update the System name and ID (must be unique) if you want/need to - since this is a green field install you should be able to use the default System ID. The only time you'd change this is if you were, for some reason, installing a new ODEE system into an existing schema that already had a system. Click Next. Enter the Assembly Line user name (default "dmkr_asline" is recommended) and set the password. Update the Assembly Line name and ID (must be unique) if you want/need to - it's quite possible that at some point you will create another assembly line, in which case you have several methods of doing so. One is to re-run the installer, and in this case you would pick a different assembly line ID and name. Click Next. Note: you can set the DB folder if needed (typically you don’t – see ODEE Installation Guide for specifics. Select the appropriate Application Server type - in this case, our green field install is going to use WebLogic - set the username to weblogic (this is required) and specify your chosen password. This credential will be used to access the application server console/control panel. Keep in mind that there are specific criteria on password choices that are required by WebLogic, but are not enforced by the installer (e.g. must contain a number, must be of a certain length, etcetera). Choose a strong password. Set the connection information for the JMS server. Note that for the 12.3.x version, the installer creates a separate JVM (WebLogic managed server) that hosts the JMS server, whereas prior editions place the JMS server on the AdminServer. You may also specify a separate URL to the JMS server in case you intend to move the JMS resources to a separate/different server (e.g. back to AdminServer). You'll need to provide a login principal and credentials - for simplicity I usually make this the same as the WebLogic domain user, however this is not a secure practice! Make your JMS principal different from the WebLogic principal and choose a strong password, then click Next. Specify the Hot Folder(s) (comma-delimited if more than one) - this is the directory/directories that is/are monitored by ODEE for jobs to process. Click Next. If you will be setting up an SMTP server for ODEE to send emails, you may configure the connection details here. The details required are simple: hostname, port, user/password, and the sender's address (e.g. emails will appear to be sent by the address shown here so if the recipient clicks "reply", this is where it will go). Click Next. If you will be using Oracle WebCenter:Content (formerly known as Oracle UCM) you can enable this option and set the endpoints/credentials here. If you aren't sure, select False - you can always go back and enable this later. I'm almost 76% certain there will be a post sometime in the future that details how to configure ODEE + WCC:C! Click Next. If you will be using Oracle UMS for sending MMS/text messages, you can enable and set the endpoints/credentials here. As with UCM, if you're not sure, don't enable it - you can always set it later. Click Next. On this screen you can change the endpoints for the Documaker Web Service (DWS), and the endpoints for approval processing in Documaker Interactive. The deployment process for ODEE will create 3 managed WebLogic servers for hosting various Documaker components (JMS, Interactive, DWS, Dashboard, Documaker Administrator, etcetera) and it will set the ports used for each of these services. In this screen you can change these values if you know how you want to deploy these managed servers - but for now we'll just accept the defaults. Click Next. Verify the installation details and click Install. You can save the installation into a response file if you need to (which might be useful if you want to rerun this installation in an unattended fashion). Allow the installation to progress... Click Next. You can save the response file if needed (e.g. in case you forgot to save it earlier!) Click Finish. That's it, you're done with the initial installation. Have a look around the ODEE_HOME that you just installed (remember we selected c:\oracle\odee_1?) and look at the files that are laid down. Don't change anything just yet! Stay tuned for the next segment where we complete and verify the installation.

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Strange: Planner takes decision with lower cost, but (very) query long runtime

- by S38

Facts: PGSQL 8.4.2, Linux I make use of table inheritance Each Table contains 3 million rows Indexes on joining columns are set Table statistics (analyze, vacuum analyze) are up-to-date Only used table is "node" with varios partitioned sub-tables Recursive query (pg = 8.4) Now here is the explained query: WITH RECURSIVE rows AS ( SELECT * FROM ( SELECT r.id, r.set, r.parent, r.masterid FROM d_storage.node_dataset r WHERE masterid = 3533933 ) q UNION ALL SELECT * FROM ( SELECT c.id, c.set, c.parent, r.masterid FROM rows r JOIN a_storage.node c ON c.parent = r.id ) q ) SELECT r.masterid, r.id AS nodeid FROM rows r QUERY PLAN ----------------------------------------------------------------------------------------------------------------------------------------------------------------- CTE Scan on rows r (cost=2742105.92..2862119.94 rows=6000701 width=16) (actual time=0.033..172111.204 rows=4 loops=1) CTE rows -> Recursive Union (cost=0.00..2742105.92 rows=6000701 width=28) (actual time=0.029..172111.183 rows=4 loops=1) -> Index Scan using node_dataset_masterid on node_dataset r (cost=0.00..8.60 rows=1 width=28) (actual time=0.025..0.027 rows=1 loops=1) Index Cond: (masterid = 3533933) -> Hash Join (cost=0.33..262208.33 rows=600070 width=28) (actual time=40628.371..57370.361 rows=1 loops=3) Hash Cond: (c.parent = r.id) -> Append (cost=0.00..211202.04 rows=12001404 width=20) (actual time=0.011..46365.669 rows=12000004 loops=3) -> Seq Scan on node c (cost=0.00..24.00 rows=1400 width=20) (actual time=0.002..0.002 rows=0 loops=3) -> Seq Scan on node_dataset c (cost=0.00..55001.01 rows=3000001 width=20) (actual time=0.007..3426.593 rows=3000001 loops=3) -> Seq Scan on node_stammdaten c (cost=0.00..52059.01 rows=3000001 width=20) (actual time=0.008..9049.189 rows=3000001 loops=3) -> Seq Scan on node_stammdaten_adresse c (cost=0.00..52059.01 rows=3000001 width=20) (actual time=3.455..8381.725 rows=3000001 loops=3) -> Seq Scan on node_testdaten c (cost=0.00..52059.01 rows=3000001 width=20) (actual time=1.810..5259.178 rows=3000001 loops=3) -> Hash (cost=0.20..0.20 rows=10 width=16) (actual time=0.010..0.010 rows=1 loops=3) -> WorkTable Scan on rows r (cost=0.00..0.20 rows=10 width=16) (actual time=0.002..0.004 rows=1 loops=3) Total runtime: 172111.371 ms (16 rows) (END) So far so bad, the planner decides to choose hash joins (good) but no indexes (bad). Now after doing the following: SET enable_hashjoins TO false; The explained query looks like that: QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- CTE Scan on rows r (cost=15198247.00..15318261.02 rows=6000701 width=16) (actual time=0.038..49.221 rows=4 loops=1) CTE rows -> Recursive Union (cost=0.00..15198247.00 rows=6000701 width=28) (actual time=0.032..49.201 rows=4 loops=1) -> Index Scan using node_dataset_masterid on node_dataset r (cost=0.00..8.60 rows=1 width=28) (actual time=0.028..0.031 rows=1 loops=1) Index Cond: (masterid = 3533933) -> Nested Loop (cost=0.00..1507822.44 rows=600070 width=28) (actual time=10.384..16.382 rows=1 loops=3) Join Filter: (r.id = c.parent) -> WorkTable Scan on rows r (cost=0.00..0.20 rows=10 width=16) (actual time=0.001..0.003 rows=1 loops=3) -> Append (cost=0.00..113264.67 rows=3001404 width=20) (actual time=8.546..12.268 rows=1 loops=4) -> Seq Scan on node c (cost=0.00..24.00 rows=1400 width=20) (actual time=0.001..0.001 rows=0 loops=4) -> Bitmap Heap Scan on node_dataset c (cost=58213.87..113214.88 rows=3000001 width=20) (actual time=1.906..1.906 rows=0 loops=4) Recheck Cond: (c.parent = r.id) -> Bitmap Index Scan on node_dataset_parent (cost=0.00..57463.87 rows=3000001 width=0) (actual time=1.903..1.903 rows=0 loops=4) Index Cond: (c.parent = r.id) -> Index Scan using node_stammdaten_parent on node_stammdaten c (cost=0.00..8.60 rows=1 width=20) (actual time=3.272..3.273 rows=0 loops=4) Index Cond: (c.parent = r.id) -> Index Scan using node_stammdaten_adresse_parent on node_stammdaten_adresse c (cost=0.00..8.60 rows=1 width=20) (actual time=4.333..4.333 rows=0 loops=4) Index Cond: (c.parent = r.id) -> Index Scan using node_testdaten_parent on node_testdaten c (cost=0.00..8.60 rows=1 width=20) (actual time=2.745..2.746 rows=0 loops=4) Index Cond: (c.parent = r.id) Total runtime: 49.349 ms (21 rows) (END) - incredibly faster, because indexes were used. Notice: Cost of the second query ist somewhat higher than for the first query. So the main question is: Why does the planner make the first decision, instead of the second? Also interesing: Via SET enable_seqscan TO false; i temp. disabled seq scans. Than the planner used indexes and hash joins, and the query still was slow. So the problem seems to be the hash join. Maybe someone can help in this confusing situation? thx, R.

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What does SQL Server execution plan show?

- by tim

There is the following code: declare @XmlData xml = '<Locations> <Location rid="1"/> </Locations>' declare @LocationList table (RID char(32)); insert into @LocationList(RID) select Location.RID.value('@rid','CHAR(32)') from @XmlData.nodes('/Locations/Location') Location(RID) insert into @LocationList(RID) select A2RID from tblCdbA2 Table tblCdbA2 has 172810 rows. I have executed the batch in SSMS with “Include Actual execution plan “ and having Profiler running. The plan shows that the first query cost is 88% relative to the batch and the second is 12%, but the profiler says that durations of the first and second query are 17ms and 210 ms respectively, the overall time is 229, which is not 12 and 88.. What is going on? Is there a way how I can determine in the execution plan which is the slowest part of the query?

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LOAD DATA INFILE not working in mariadb

- by Haseena

Iam trying to migrate from mysql to mariadb. On this time I can face an issue with mariadb. When I can trying to load a data file into a table, it shows an error like : SQL Error (29): File 'C:/Documents and Settings/Administrator/Local Settings/Temp/SAMPLE/DATA_TEMP1351761841668/SampleFile0' not found (Errcode: 2) But the file already exists in the path.... Another one point is that the same command successfully works with MySQL. Is MariaDB has any permission issue? Login as Administrator. See below my query : load data infile "'C:/Documents and Settings/Administrator/Local Settings/Temp/SAMPLE/DATA_TEMP1351761841668/SampleFile0" into table SAMPLETABLE; When changing the path loke "C:/SampleFile0", its working properly. From Administrator folder it doesn't working. Can anyone help me in this regard??? Iam a newone in MariaDB.

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MYSQL query to get all entries with specific time, from PHP?

- by meds

I'm trying to query a mysql table which places its date in the following format: yyyy-mm-dd hh:mm:ss So it's date and time, and that's all in a single field. Now from php I want to get the time and query the table to only return entries where the date field is less than 24 hours old. I'm having issues with the system because PHPs get time seems to return the values seperately and I'm struggling to figure out how to make it work with mysql queries. This seems fairly simple but I'm quite new to php so sorry if I'm completely missing something..

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SQL count NULL cells

- by Giuseppe

Dear All, I have the following problem. I have a table in a db, with many columns. I can do different kind of select queries, to show, for example, for each record that satisfies a condition: all cells from columns with names ending in _t0 all cells from columns with names ending in _t1 ... To get the column lists to form the queries I use the information schema. Now, the problem: each query returns a record with a subset of the columns of the big table. This means that I can get a row of (all!) NULLs. How can I ask my query to reject such rows without having to type in explicitely the column names (i.e. by saying where col_1 is not null, col_2 is not null...)? Is it possible? Thanks in advance!!! Sep

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LRU caches in C

- by lazyconfabulator

I need to cache a large (but variable) number of smallish (1 kilobyte to 10 megabytes) files in memory, for a C application (in a *nix environment). Since I don't want to eat all my memory, I'd like to set hard memory limit (say, 64 megabytes) and push files into a hash table with the file name as the key and dispose of the entries with the least use. What I believe I need is an LRU cache. Really, I'd rather not roll my own so if someone knows where I can find a workable library, please point the way? Failing that, can someone provide a simple example of an LRU cache in C? Related posts indicated that a hash table with a doubly-linked list, but I'm not even clear on how a doubly-linked list keeps LRU. Side note: I realize this is almost exactly the function of memcache, but it's not an option for me. I also took a look at the source hoping to enlighten myself on LRU caching, with no success.

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Using memtables in sql. When is it reasonable and is it safe?

- by Spiros

I was just reading an update from a friend's project, mentioning the use of memtables to store data temporatily and then flush to a table on disk. Up to now, I have never faced a situation where I would use a memtable, or a situation where I would think the use of a mem table would be beneficial; so I wonder, when would someone use mem tables? what makes a memtable (appart from access speed) a reasonable choice? and how safe is it, even for temp data? there is always the limitation of available physical memory.

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How to combine two sql queries?

- by plasmuska

Hi Guys, I have a stock table and I would like to create a report that will show how often were items ordered. "stock" table: item_id | pcs | operation apples | 100 | order oranges | 50 | order apples | -100 | delivery pears | 100 | order oranges | -40 | delivery apples | 50 | order apples | 50 | delivery Basically I need to join these two queries together. A query which prints stock balances: SELECT stock.item_id, Sum(stock.pcs) AS stock_balance FROM stock GROUP BY stock.item_id; A query which prints sales statistics SELECT stock.item_id, Sum(stock.pcs) AS pcs_ordered, Count(stock.item_id) AS number_of_orders FROM stock GROUP BY stock.item_id, stock.operation HAVING stock.operation="order"; I think that some sort of JOIN would do the job but I have no idea how to glue queries together. Desired output: item_id | stock_balance | pcs_ordered | number_of_orders apples | 0 | 150 | 2 oranges | 10 | 50 | 1 pears | 100 | 100 | 1 This is just example. Maybe, I will need to add more conditions because there is more columns. Is there a universal technique of combining multiple queries together?

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How active record is automatically setting up the autoincremental value of ID?

- by piemesons

Here this is what we are doing:-- an_order = Order.new an_order.name = "Dave Thomas" an_order.email = "[email protected]" an_order.address = "123 Main St" an_order.pay_type = "check" an_order.save Now it will insert a new row in orders table right. I m having a ID column in that table. Now suppose after inserting this record the value of the ID corresponding to this record is 100. Now how this 100 value came to know? Does the previous value of ID ie 99 (Suppose) is stored somewhere in some variable/file in the ORM layer or before inserting this value a query was fired to know about the last inserted value or database is itself doing that or anything else???

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MarkupBuilder using list

- by tathamr

I am currently using sql.row("statement") and storing to a list. I then am trying to setup my xml file using MarkupBuilder. Is there a better way than iterating over the list poping off an item and then parsing it to add my different column names and values? What is stored by list entry is ID='X' Period='Yearly' Lengh='test' So the XML would be something similar to: <table name='test'> <row> <column name=ID>X</column> <column name=Period>Yearly</column> <column name=Length>test</column> </row> </table>

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How does void QTableWidget::setItemPrototype ( const QTableWidgetItem * item ) clones objects?

- by chappar

QTableWidget::setItemPrototype says following. "The table widget will use the item prototype clone function when it needs to create a new table item. For example when the user is editing in an empty cell. This is useful when you have a QTableWidgetItem subclass and want to make sure that QTableWidget creates instances of your subclass." How does this actually work as you can pass any of the QTableWidgetItem subclass pointer to setItemPrototype and at run time there is no way you can get the size of an object having just pointer to it?

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