sql - SQLite join optimisation -

-

if have query such as:

select a.name, a.description inner join b on a.id1 = b.id1 inner join c on b.id2 = c.id2 group a.name, a.description

what optimal columns index query in sqlite if consider there on 100,000 rows in each of tables?

the reason ask not performance query group expect rdbms (sql server) when apply same optimisation.

would right in thinking columns referenced on single table in query in sqlite need included in single composite index best performance?

the problem you're expecting sqlite have same performance characteristics full rdbms. won't. sqllite doesn't have luxury of getting cache quite in memory, has rebuild cache every time run application, limited set number of cores, etc, etc, etc. tradeoffs using embedded rdbms on full one.

as far optimizations go, try indexing lookup columns , test. try creating covering index. sure test both selects , code paths update database, you're speeding 1 @ expense of other. find indexing gives best balance between 2 needs , go it.


Comments

Post a Comment

Popular posts from this blog

android - Spacing between the stars of a rating bar? -

-
ho can set spacing beween stars? thats ratingbar: ratingbar = (ratingbar) inflater.inflate(r.layout.ratingbar, null); ratingbar.setlayoutparams(new layoutparams(layoutparams.wrap_content, layoutparams.wrap_content)); the layout: <?xml version="1.0" encoding="utf-8"?> <ratingbar xmlns:android="http://schemas.android.com/apk/res/android" style="@style/mystyle" android:layout_alignparentright="true" android:layout_height="19dp" android:layout_width="wrap_content" android:numstars="5"> </ratingbar> the style: <style name="mystyle" parent="@android:style/widget.ratingbar"> <item name="android:progressdrawable">@drawable/android_r2_ratingstar_yellow</item> <item name="android:indeterminatedrawable">@drawable/android_r2_ratingstar_grey</item> </style> thanks, cheers you have
Read more

aspxgridview - Devexpress grid - header filter does not work if column is initially hidden -

-
i'm using devexpress grid , i'm trying 'country' column display header filter properly: <dx:gridviewdatacolumn caption="country" fieldname="countryname" showincustomizationform="true" visible="false"> <settings allowheaderfilter="true"/> </dx:gridviewdatacolumn> if 'country' column set visible='true', header filter displayed should(it shows value option list). however, want 'country' column hidden, available in customization window(like in code above). in case, when column dragged outside customization window , grid , header filter clicked, javascript error encountered: element null element.addeventlistener(eventname, func, true); is known bug? there workarounds? set aspxgridview.settings.showheaderfilterbutton property true resolve problem. the following markup works fine me (i using dxperience 10.1.7): <asp:accessdatasource id="accessda
Read more

c# - How to execute a particular part of code asynchronously in a class -

-
i creating speech recognition engine that's going respond user commands.i have created button enable , disable speech recognition per user convenience.i have used dispose() of speech engine disable speech recoginition.here code private void button1_click(object sender, routedeventargs e) { engineon = !engineon; if (engineon) { speechengine = speech.createspeechengine(); //speech class creates , returns new speech engine. speechengine.audiolevelupdated += new eventhandler<audiolevelupdatedeventargs>(speechengine_audiolevelupdated); // use system's default microphone speechengine.setinputtodefaultaudiodevice(); speechengine.loadgrammar(new dictationgrammar()); // start listening speechengine.recognizeasync(recognizemode.multiple); } else { speechclass.myengine.dispose(); } } but disposal of speech obj
Read more