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  • Is there a faster TList implementation ?

    - by dmauric.mp
    My application makes heavy use of TList, so I was wondering if there are any alternative implementations that are faster or optimized for particular use case. I know of RtlVCLOptimize.pas 2.77, which has optimized implementations of several TList methods. But I'd like to know if there is anything else out there. I also don't require it to be a TList descendant, I just need the TList functionality regardless of how it's implemented. It's entirely possible, given the rather basic functionality TList provides, that there is not much room for improvement, but would still like to verify that, hence this question.

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  • MySQL won't use index for query?

    - by Jack Sleight
    I have this table: CREATE TABLE `point` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `siteid` INT(11) NOT NULL, `lft` INT(11) DEFAULT NULL, `rgt` INT(11) DEFAULT NULL, `level` SMALLINT(6) DEFAULT NULL, PRIMARY KEY (`id`), KEY `point_siteid_site_id` (`siteid`), CONSTRAINT `point_siteid_site_id` FOREIGN KEY (`siteid`) REFERENCES `site` (`id`) ON DELETE CASCADE ) ENGINE=INNODB AUTO_INCREMENT=35 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci And this query: SELECT * FROM `point` WHERE siteid = 1; Which results in this EXPLAIN information: +----+-------------+-------+------+----------------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+----------------------+------+---------+------+------+-------------+ | 1 | SIMPLE | point | ALL | point_siteid_site_id | NULL | NULL | NULL | 6 | Using where | +----+-------------+-------+------+----------------------+------+---------+------+------+-------------+ Question is, why isn't the query using the point_siteid_site_id index?

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  • "Anagram solver" based on statistics rather than a dictionary/table?

    - by James M.
    My problem is conceptually similar to solving anagrams, except I can't just use a dictionary lookup. I am trying to find plausible words rather than real words. I have created an N-gram model (for now, N=2) based on the letters in a bunch of text. Now, given a random sequence of letters, I would like to permute them into the most likely sequence according to the transition probabilities. I thought I would need the Viterbi algorithm when I started this, but as I look deeper, the Viterbi algorithm optimizes a sequence of hidden random variables based on the observed output. I am trying to optimize the output sequence. Is there a well-known algorithm for this that I can read about? Or am I on the right track with Viterbi and I'm just not seeing how to apply it?

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  • How can I Query only __key__ on a Google Appengine PolyModel child?

    - by Gabriel
    So the situation is: I want to optimize my code some for doing counting of records. So I have a parent Model class Base, a PolyModel class Entry, and a child class of Entry Article: How would I query Article.key so I can reduce the query load but only get the Article count. My first thought was to use: q = db.GqlQuery("SELECT __key__ from Article where base = :1", i_base) but it turns out GqlQuery doesn't like that because articles are actually stored in a table called Entry. Would it be possible to Query the class attribute? something like: q = db.GqlQuery("select __key__ from Entry where base = :1 and :2 in class", i_base, 'Article') neither of which work. Turns out the answer is even easier. But I am going to finish this question because I looked everywhere for this. q = db.GqlQuery("select __key__ from Entry where base = :1 and class = :2", i_base, 'Article')

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  • Nodes set of the same type with if-test. Make it less.

    - by Kalinin
    How to make the code more beautiful (compact)? <xsl:template match="part"> <table class="part"> <xsl:if test="name != ''"> <tr> <td>????????</td><td><xsl:value-of select="name"/></td> </tr> </xsl:if> <xsl:if test="model != ''"> <tr> <td>??????</td><td><xsl:value-of select="model"/></td> </tr> </xsl:if> <xsl:if test="year != ''"> <tr> <td>???</td><td><xsl:value-of select="year"/></td> </tr> </xsl:if> <xsl:if test="glass_type != ''"> <tr> <td>???</td><td><xsl:value-of select="glass_type"/></td> </tr> </xsl:if> <xsl:if test="scancode != ''"> <tr> <td>???????</td><td><xsl:value-of select="scancode"/></td> </tr> </xsl:if> <xsl:if test="eurocode != ''"> <tr> <td>???????</td><td><xsl:value-of select="eurocode"/></td> </tr> </xsl:if> <xsl:if test="coment != ''"> <tr> <td>???????????</td><td><xsl:value-of select="coment"/></td> </tr> </xsl:if> <xsl:if test="glass_size != ''"> <tr> <td>??????</td><td><xsl:value-of select="glass_size"/></td> </tr> </xsl:if> <xsl:if test="vendor != ''"> <tr> <td>?????????????</td><td><xsl:value-of select="vendor"/></td> </tr> </xsl:if> <xsl:if test="trademark != ''"> <tr> <td>???????? ?????</td><td><xsl:value-of select="trademark"/></td> </tr> </xsl:if> <xsl:if test="fprice != ''"> <tr> <td>????</td><td><xsl:value-of select="fprice"/></td> </tr> </xsl:if> </table> </xsl:template> Update: i wrote: <my:translations xmlns:my="my:my"> <w e="name" r="????????"/> <w e="model" r="??????"/> <w e="year" r="???"/> <w e="glass_type" r="???"/> <w e="scancode" r="???????"/> <w e="eurocode" r="???????"/> <w e="comment" r="???????????"/> <w e="glass_size" r="??????"/> <w e="vendor" r="?????????????"/> <w e="trademark" r="???????? ?????"/> <w e="fprice" r="????"/> </my:translations> <xsl:value-of select="//w/@r"/> And have no result from this code. Is it normal? And how can i get new element w?

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  • Why is Javascript's Math.floor the slowest way to calculate floor in Javascript?

    - by z5h
    I'm generally not a fan of microbenchmarks. But this one has a very interesting result. http://ernestdelgado.com/archive/benchmark-on-the-floor/ It suggests that Math.floor is the SLOWEST way to calculate floor in Javascript. ~~n, n|n, n&n all being faster. This seems pretty shocking as I would expect that people implementing Javascript in today's modern browsers would be some pretty smart people. Does floor do something important that the other methods fail to do? Is there any reason to use it?

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  • Why is doing a top(1) on an indexed column in SQL Server 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 (campaignid_int) 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? edit: estimated execution plan: select (0%) - top (0%) - clustered index scan (100%)

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  • Is SQL DATEDIFF(year, ..., ...) an Expensive Computation?

    - by rlb.usa
    I'm trying to optimize up some horrendously complicated SQL queries because it takes too long to finish. In my queries, I have dynamically created SQL statements with lots of the same functions, so I created a temporary table where each function is only called once instead of many, many times - this cut my execution time by 3/4. So my question is, can I expect to see much of a difference if say, 1,000 datediff computations are narrowed to 100?

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  • Will the compiler optimize escaping an inner loop?

    - by BCS
    The code I have looks like this (all uses of done shown): bool done = false; for(int i = 0; i < big; i++) { ... for(int j = 0; j < wow; j++) { ... if(foo(i,j)) { done = true; break; } ... } if(done) break; ... } will any compilers convert it to this: for(int i = 0; i < big; i++) { ... for(int j = 0; j < wow; j++) { ... if(foo(i,j)) goto __done; // same as a labeled break if we had it ... } ... } __done:;

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  • Mysql - help me optimize this query (improved question)

    - by sandeepan-nath
    About the system: - There are tutors who create classes and packs - A tags based search approach is being followed.Tag relations are created when new tutors register and when tutors create packs (this makes tutors and packs searcheable). For details please check the section How tags work in this system? below. Following is the concerned query SELECT SUM(DISTINCT( t.tag LIKE "%Dictatorship%" )) AS key_1_total_matches, SUM(DISTINCT( t.tag LIKE "%democracy%" )) AS key_2_total_matches, COUNT(DISTINCT( od.id_od )) AS tutor_popularity, CASE WHEN ( IF(( wc.id_wc > 0 ), ( wc.wc_api_status = 1 AND wc.wc_type = 0 AND wc.class_date > '2010-06-01 22:00:56' AND wccp.status = 1 AND ( wccp.country_code = 'IE' OR wccp.country_code IN ( 'INT' ) ) ), 0) ) THEN 1 ELSE 0 END AS 'classes_published', CASE WHEN ( IF(( lp.id_lp > 0 ), ( lp.id_status = 1 AND lp.published = 1 AND lpcp.status = 1 AND ( lpcp.country_code = 'IE' OR lpcp.country_code IN ( 'INT' ) ) ), 0) ) THEN 1 ELSE 0 END AS 'packs_published', td . *, u . * FROM tutor_details AS td JOIN users AS u ON u.id_user = td.id_user LEFT JOIN learning_packs_tag_relations AS lptagrels ON td.id_tutor = lptagrels.id_tutor LEFT JOIN learning_packs AS lp ON lptagrels.id_lp = lp.id_lp LEFT JOIN learning_packs_categories AS lpc ON lpc.id_lp_cat = lp.id_lp_cat LEFT JOIN learning_packs_categories AS lpcp ON lpcp.id_lp_cat = lpc.id_parent LEFT JOIN learning_pack_content AS lpct ON ( lp.id_lp = lpct.id_lp ) LEFT JOIN webclasses_tag_relations AS wtagrels ON td.id_tutor = wtagrels.id_tutor LEFT JOIN webclasses AS wc ON wtagrels.id_wc = wc.id_wc LEFT JOIN learning_packs_categories AS wcc ON wcc.id_lp_cat = wc.id_wp_cat LEFT JOIN learning_packs_categories AS wccp ON wccp.id_lp_cat = wcc.id_parent LEFT JOIN order_details AS od ON td.id_tutor = od.id_author LEFT JOIN orders AS o ON od.id_order = o.id_order LEFT JOIN tutors_tag_relations AS ttagrels ON td.id_tutor = ttagrels.id_tutor JOIN tags AS t ON ( t.id_tag = ttagrels.id_tag ) OR ( t.id_tag = lptagrels.id_tag ) OR ( t.id_tag = wtagrels.id_tag ) WHERE ( u.country = 'IE' OR u.country IN ( 'INT' ) ) AND CASE WHEN ( ( t.id_tag = lptagrels.id_tag ) AND ( lp.id_lp 0 ) ) THEN lp.id_status = 1 AND lp.published = 1 AND lpcp.status = 1 AND ( lpcp.country_code = 'IE' OR lpcp.country_code IN ( 'INT' ) ) ELSE 1 END AND CASE WHEN ( ( t.id_tag = wtagrels.id_tag ) AND ( wc.id_wc 0 ) ) THEN wc.wc_api_status = 1 AND wc.wc_type = 0 AND wc.class_date '2010-06-01 22:00:56' AND wccp.status = 1 AND ( wccp.country_code = 'IE' OR wccp.country_code IN ( 'INT' ) ) ELSE 1 END AND CASE WHEN ( od.id_od 0 ) THEN od.id_author = td.id_tutor AND o.order_status = 'paid' AND CASE WHEN ( od.id_wc 0 ) THEN od.can_attend_class = 1 ELSE 1 END ELSE 1 END GROUP BY td.id_tutor HAVING key_1_total_matches = 1 AND key_2_total_matches = 1 ORDER BY tutor_popularity DESC, u.surname ASC, u.name ASC LIMIT 0, 20 The problem The results returned by the above query are correct (AND logic working as per expectation), but the time taken by the query rises alarmingly for heavier data and for the current data I have it is like 25 seconds as against normal query timings of the order of 0.005 - 0.0002 seconds, which makes it totally unusable. It is possible that some of the delay is being caused because all the possible fields have not yet been indexed. The tag field of tags table is indexed. Is there something faulty with the query? What can be the reason behind 20+ seconds of execution time? How tags work in this system? When a tutor registers, tags are entered and tag relations are created with respect to tutor's details like name, surname etc. When a Tutors create packs, again tags are entered and tag relations are created with respect to pack's details like pack name, description etc. tag relations for tutors stored in tutors_tag_relations and those for packs stored in learning_packs_tag_relations. All individual tags are stored in tags table. The explain query output:- Please see this screenshot - http://www.test.examvillage.com/Explain_query.jpg

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  • unroll nested for loops in C++

    - by Hristo
    How would I unroll the following nested loops? for(k = begin; k != end; ++k) { for(j = 0; j < Emax; ++j) { for(i = 0; i < N; ++i) { if (j >= E[i]) continue; array[k] += foo(i, tr[k][i], ex[j][i]); } } } I tried the following, but my output isn't the same, and it should be: for(k = begin; k != end; ++k) { for(j = 0; j < Emax; ++j) { for(i = 0; i+4 < N; i+=4) { if (j >= E[i]) continue; array[k] += foo(i, tr[k][i], ex[j][i]); array[k] += foo(i+1, tr[k][i+1], ex[j][i+1]); array[k] += foo(i+2, tr[k][i+2], ex[j][i+2]); array[k] += foo(i+3, tr[k][i+3], ex[j][i+3]); } if (i < N) { for (; i < N; ++i) { if (j >= E[i]) continue; array[k] += foo(i, tr[k][i], ex[j][i]); } } } } I will be running this code in parallel using Intel's TBB so that it takes advantage of multiple cores. After this is finished running, another function prints out what is in array[] and right now, with my unrolling, the output isn't identical. Any help is appreciated. Thanks, Hristo

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  • Long-running Database Query

    - by JamesMLV
    I have a long-running SQL Server 2005 query that I have been hoping to optimize. When I look at the actual execution plan, it says a Clustered Index Seek has 66% of the cost. Execuation Plan Snippit: <RelOp AvgRowSize="31" EstimateCPU="0.0113754" EstimateIO="0.0609028" EstimateRebinds="0" EstimateRewinds="0" EstimateRows="10198.5" LogicalOp="Clustered Index Seek" NodeId="16" Parallel="false" PhysicalOp="Clustered Index Seek" EstimatedTotalSubtreeCost="0.0722782"> <OutputList> <ColumnReference Database="[wf_1]" Schema="[dbo]" Table="[Indices]" Alias="[I]" Column="quoteDate" /> <ColumnReference Database="[wf_1]" Schema="[dbo]" Table="[Indices]" Alias="[I]" Column="price" /> <ColumnReference Database="[wf_1]" Schema="[dbo]" Table="[Indices]" Alias="[I]" Column="tenure" /> </OutputList> <RunTimeInformation> <RunTimeCountersPerThread Thread="0" ActualRows="1067" ActualEndOfScans="1" ActualExecutions="1" /> </RunTimeInformation> <IndexScan Ordered="true" ScanDirection="FORWARD" ForcedIndex="false" NoExpandHint="false"> <DefinedValues> <DefinedValue> <ColumnReference Database="[wf_1]" Schema="[dbo]" Table="[Indices]" Alias="[I]" Column="quoteDate" /> </DefinedValue> <DefinedValue> <ColumnReference Database="[wf_1]" Schema="[dbo]" Table="[Indices]" Alias="[I]" Column="price" /> </DefinedValue> <DefinedValue> <ColumnReference Database="[wf_1]" Schema="[dbo]" Table="[Indices]" Alias="[I]" Column="tenure" /> </DefinedValue> </DefinedValues> <Object Database="[wf_1]" Schema="[dbo]" Table="[Indices]" Index="[_dta_index_Indices_14_320720195__K5_K2_K1_3]" Alias="[I]" /> <SeekPredicates> <SeekPredicate> <Prefix ScanType="EQ"> <RangeColumns> <ColumnReference Database="[wf_1]" Schema="[dbo]" Table="[Indices]" Alias="[I]" Column="HedgeProduct" ComputedColumn="true" /> </RangeColumns> <RangeExpressions> <ScalarOperator ScalarString="(1)"> <Const ConstValue="(1)" /> </ScalarOperator> </RangeExpressions> </Prefix> <StartRange ScanType="GE"> <RangeColumns> <ColumnReference Database="[wf_1]" Schema="[dbo]" Table="[Indices]" Alias="[I]" Column="tenure" /> </RangeColumns> <RangeExpressions> <ScalarOperator ScalarString="[@StartMonth]"> <Identifier> <ColumnReference Column="@StartMonth" /> </Identifier> </ScalarOperator> </RangeExpressions> </StartRange> <EndRange ScanType="LE"> <RangeColumns> <ColumnReference Database="[wf_1]" Schema="[dbo]" Table="[Indices]" Alias="[I]" Column="tenure" /> </RangeColumns> <RangeExpressions> <ScalarOperator ScalarString="[@EndMonth]"> <Identifier> <ColumnReference Column="@EndMonth" /> </Identifier> </ScalarOperator> </RangeExpressions> </EndRange> </SeekPredicate> </SeekPredicates> </IndexScan> </RelOp> From this, does anyone see an obvious problem that would be causing this to take so long? Here is the query: (SELECT quotedate, tenure, price, ActualVolume, HedgePortfolioValue, Price AS UnhedgedPrice, ((ActualVolume*Price - HedgePortfolioValue)/ActualVolume) AS HedgedPrice FROM ( SELECT [quoteDate] ,[price] , tenure ,isnull(wf_1.[Risks].[HedgePortValueAsOfDate2](1,tenureMonth,quotedate,price),0) as HedgePortfolioValue ,[TotalOperatingGasVolume] as ActualVolume FROM [wf_1].[dbo].[Indices] I inner join ( SELECT DISTINCT tenureMonth FROM [wf_1].[Risks].[KnowRiskTrades] WHERE HedgeProduct = 1 AND portfolio <> 'Natural Gas Hedge Transactions' ) B ON I.tenure=B.tenureMonth inner join ( SELECT [Month],[TotalOperatingGasVolume] FROM [wf_1].[Risks].[ActualGasVolumes] ) C ON C.[Month]=B.tenureMonth WHERE HedgeProduct = 1 AND quoteDate>=dateadd(day, -3*365, tenureMonth) AND quoteDate<=dateadd(day,-3,tenureMonth) )A )

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  • Verifying compiler optimizations in gcc/g++ by analyzing assembly listings

    - by Victor Liu
    I just asked a question related to how the compiler optimizes certain C++ code, and I was looking around SO for any questions about how to verify that the compiler has performed certain optimizations. I was trying to look at the assembly listing generated with g++ (g++ -c -g -O2 -Wa,-ahl=file.s file.c) to possibly see what is going on under the hood, but the output is too cryptic to me. What techniques do people use to tackle this problem, and are there any good references on how to interpret the assembly listings of optimized code or articles specific to the GCC toolchain that talk about this problem?

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  • Resize an image and maintain quality?

    - by JasonS
    Hi, I have a problem with resizing images. What happens is that if you upload a file larger than the stated parameters, the image is cropped, then saved at 100% quality. So if I upload a large jpeg which is 272Kb. The image is cropped by 100 odd pixels. The file size then goes up to 1.2Mb. We are saving images at a 100% quality. I assume that this is what is causing the problem. The image is exported from Photoshop at 30% quality which reduces the file size. Resaving the image at 100% quality creates the same image but I assume with a lot of redundant file data. Has anyone encountered this before? Does anyone have a solution? This is what we are using. $source_im = imagecreatefromjpeg ($file); $dest_im = imagecreatetruecolor ($newsize_x, $newsize_y); imagecopyresampled ( $dest_im, $source_im, 0, 0, $offset_x, $offset_y, $newsize_x, $newsize_y, $sourceWidth, $sourceHeight ); imagedestroy ($source_im); if ($greyscale) { $dest_im = $this->imageconvertgreyscale ($dest_im); } imagejpeg($dest_im, $save_to_file, $quality); break;

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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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  • What algorithm can I use to determine points within a semi-circle?

    - by khayman218
    I have a list of two-dimensional points and I want to obtain which of them fall within a semi-circle. Originally, the target shape was a rectangle aligned with the x and y axis. So the current algorithm sorts the pairs by their X coord and binary searches to the first one that could fall within the rectangle. Then it iterates over each point sequentially. It stops when it hits one that is beyond both the X and Y upper-bound of the target rectangle. This does not work for a semi-circle as you cannot determine an effective upper/lower x and y bounds for it. The semi-circle can have any orientation. Worst case, I will find the least value of a dimension (say x) in the semi-circle, binary search to the first point which is beyond it and then sequentially test the points until I get beyond the upper bound of that dimension. Basically testing an entire band's worth of points on the grid. The problem being this will end up checking many points which are not within the bounds.

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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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  • How to increase query speed without using full-text search?

    - by andre matos
    This is my simple query; By searching selectnothing I'm sure I'll have no hits. SELECT nome_t FROM myTable WHERE nome_t ILIKE '%selectnothing%'; This is the EXPLAIN ANALYZE VERBOSE Seq Scan on myTable (cost=0.00..15259.04 rows=37 width=29) (actual time=2153.061..2153.061 rows=0 loops=1) Output: nome_t Filter: (nome_t ~~* '%selectnothing%'::text) Total runtime: 2153.116 ms myTable has around 350k rows and the table definition is something like: CREATE TABLE myTable ( nome_t text NOT NULL, ) I have an index on nome_t as stated below: CREATE INDEX idx_m_nome_t ON myTable USING btree (nome_t); Although this is clearly a good candidate for Fulltext search I would like to rule that option out for now. This query is meant to be run from a web application and currently it's taking around 2 seconds which is obviously too much; Is there anything I can do, like using other index methods, to improve the speed of this query?

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  • MySQL Paritioning performance

    - by Imran Pathan
    Measured performance on key partitioned tables and normal tables separately. But we couldn't find any performance improvement with partitioning. Queries are pruned. Using MySQL 5.1.47 on RHEL 4. Table details: UserUsage - Will have entries for user mobile number and data usage for each date. Mobile number and Date as PRI KEY. UserProfile - Queries prev table and stores summary for each mobile number. Mobile number PRI KEY. CREATE TABLE `UserUsage` ( `Msisdn` decimal(20,0) NOT NULL, `Date` date NOT NULL, . . PRIMARY KEY USING BTREE (`Msisdn`,`Date`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 PARTITION BY KEY(Msisdn) PARTITIONS 50; CREATE TABLE `UserProfile` ( `Msisdn` decimal(20,0) NOT NULL, . . PRIMARY KEY (`Msisdn`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 PARTITION BY KEY(Msisdn) PARTITIONS 50; Second table is updated by query select and order by date in first table in a perl program, query is select * from UserUsage where Msisdn=number order by Date desc limit 7 [Process data in perl] update UserProfile values(....) where Msisdn=number explain partition for select, shows row being scanned in a particular partition only. Is something wrong with partition design or queries as partitioning is taking almost same or more time compared to normal tables?

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  • Is a program compiled with -g gcc flag slower than the same program compiled without -g?

    - by e271p314
    I'm compiling a program with -O3 for performance and -g for debug symbols (in case of crash I can use the core dump). One thing bothers me a lot, does the -g option results in a performance penalty? When I look on the output of the compilation with and without -g, I see that the output without -g is 80% smaller than the output of the compilation with -g. If the extra space goes for the debug symbols, I don't care about it (I guess) since this part is not used during runtime. But if for each instruction in the compilation output without -g I need to do 4 more instructions in the compilation output with -g than I certainly prefer to stop using -g option even at the cost of not being able to process core dumps. How to know the size of the debug symbols section inside the program and in general does compilation with -g creates a program which runs slower than the same code compiled without -g?

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  • Which fieldtype is best for storing PRICE values?

    - by BerggreenDK
    Hi there I am wondering whats the best "price field" in MSSQL for a shoplike structure? Looking at this overview: http://www.teratrax.com/sql_guide/data_types/sql_server_data_types.html We have datatypes called money, smallmoney, then we have decimal/numeric and lastly float and real Name, memory/disk-usage and value ranges: Money: 8 bytes (values: -922,337,203,685,477.5808 to +922,337,203,685,477.5807) Smallmoney: 4 bytes (values: -214,748.3648 to +214,748.3647) Decimal: 9 [default, min. 5] bytes (values: -10^38 +1 to 10^38 -1 ) Float: 8 bytes (values: -1.79E+308 to 1.79E+308 ) Real: 4 bytes (values: -3.40E+38 to 3.40E+38 ) My question is: is it really wise to store pricevalues in those types? what about eg. INT? Int: 4 bytes (values: -2,147,483,648 to 2,147,483,647) Lets say a shop uses dollars, they have cents, but I dont see prices being $49.2142342 so the use of a lot of decimals showing cents seems waste of SQL bandwidth. Secondly, most shops wouldn't show any prices near 200.000.000 (not in normal webshops at least... unless someone is trying to sell me a famous tower in Paris) So why not go for an int? An int is fast, its only 4 bytes and you can easily make decimals, by saving values in cents instead of dollars and then divide when you present the values. The other approach would be to use smallmoney which is 4 bytes too, but this will require the math part of the CPU to do the calc, where as Int is integer power... on the downside you will need to divide every single outcome. Are there any "currency" related problems with regionalsettings when using smallmoney/money fields? what will these transfer too in C#/.NET ? Any pros/cons? Go for integer prices or smallmoney or some other? Whats does your experience tell?

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  • Optimizing BeautifulSoup (Python) code

    - by user283405
    I have code that uses the BeautifulSoup library for parsing, but it is very slow. The code is written in such a way that threads cannot be used. Can anyone help me with this? I am using BeautifulSoup for parsing and than save into a DB. If I comment out the save statement, it still takes a long time, so there is no problem with the database. def parse(self,text): soup = BeautifulSoup(text) arr = soup.findAll('tbody') for i in range(0,len(arr)-1): data=Data() soup2 = BeautifulSoup(str(arr[i])) arr2 = soup2.findAll('td') c=0 for j in arr2: if str(j).find("<a href=") > 0: data.sourceURL = self.getAttributeValue(str(j),'<a href="') else: if c == 2: data.Hits=j.renderContents() #and few others... c = c+1 data.save() Any suggestions? Note: I already ask this question here but that was closed due to incomplete information.

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