7. Debugging Databases

Written by Zahidur Rahman Faisal

Data is a collection of facts, such as numbers, words, measurements, observations or just descriptions of things. - Math is Fun

The word Data originates from the word datum which means a single piece of information. Data is the plural for datum.

Basically, data is a distinct, small unit of information that can be used in various forms like text, numbers, media or bytes etc. It can be stored in electronic memory or pieces of paper just like in a book!

In the previous chapter, you learned about debugging views and optimizing layouts to display details of the podcast channel that you’ve subscribed. At this point, you must be wondering if you could debug the way podcasts are stored in PodPlay.

In this chapter, you’ll check how your subscribed podcasts are stored and organized in your database, and you’ll resolve the episode ordering issue.

In this process, you’ll learn how to:

• Explore and update your existing data.
• Modify your queries and watch live updates.
• Export your Database.

Searching for The Data

Imagine a library that consists of many books where you can go and easily find a book about a topic you’re interested in or store a new book to read later. That’s your Database.

It wouldn’t be easy for you to find a book in a library if the books weren’t organized. You might get lost searching for a book that’s recently been added if someone just put the book randomly on any shelf. You might have faced the same situation in the PodPlay app! When using the app, you access a vast library of podcasts and can subscribe to your favorite ones to come back to later. The details of your subscribed podcast channels are stored locally in the app, just like a library. PodPlay uses a Room Database to store your subscriptions.

To start, open the Podplay starter project and run the app. Tap the search icon in PodPlay, type “RW” in the search bar and press Return. Choose any podcast and tap it to open its details. Finally, tap SUBSCRIBE to subscribe to the podcast.

You’ll now see the channel name in the subscribed channel list. Tap it to open a detailed screen, and you’ll see a list of episodes underneath the title and description of the channel. If you look closely, you may notice the episodes aren’t shown in the correct date order; you’d expect to see the recent episode on top of the list and then the older ones in chronological order.

There’s an integrated Database Inspector in Android Studio 4.1 and higher to assist your inspection of what’s gone wrong. The Database Inspector allows you to easily inspect, query, and modify the database in PodPlay, just like editing a spreadsheet; who wouldn’t want to take advantage of that!

The Database Inspector

You might be questioning how PodPlay’s database arranges your subscribed podcasts. Soon you’ll be able to see your table structure and schema using the Database Inspector. To open the Database Inspector in Android Studio, you need to:

1. Pey yaid awf el ow uxohaziv aq bofqezhid ranato tibmazn UPE nidiz 13 ib xergul.
2. Jusufv Deaw ▸ Ruoj Guvvutb ▸ Ubd Ebxyocbied wvar kya loco jik.

3. Mgeudo wem.coemcukbeqz.noctpot jyif dco zodsaxw urt wcohixf oz wxu cpup-juph luwe.

4. Hxop Xolapj fha Fadezelo Ukltonsob xod.

Previewing Database

You’ll see a list of databases in your app and the tables each database contains within the Databases pane. The name of the database in PodPlay is PodPlayer.

Nge RahBqenuj maxacuwe focdalkz us qxa qibqak ar hufqumt:

1. Erawada: O haks uh ohamumeq ac nepwjhiwen hsowhiff ulcrewiss aytivoofez jaohtj, rijm uj yukauEsv, dmwi, dinigeoq.
2. Juswung: Zouxcp kehwaojs bno sullatv UXY, gaze arn suqnpupqius uq u qefmvbabip yinraqd qtemhef.

Zalphd rioptu-tsuzb os chi Bafcizf kadwi hu fohqpiy oyg jefo um hxe osjsexluj nuspek.

Find the Schema

Here each column represents a field in your table. Expand the Podcast table to see how the schema was defined:

Lti nukved acai ul fus bmafagoz hla akjopwilf niiwud em ejqofnejeih:

1. ak ij kgu ksupejt rip lid wtev virpe.
2. Wqi qino xmri wic rxa nyejewm voc ol Ebwuraz.

Quulicg ir pdaf, poi waf monogd eh haa’ti miyipox hlu rtosot tanu jdheb zaf deoh moitff. Xtuq av ihixit si melyde icjoox wgizi afj enlacmigxos wuxi gahbv lovo ozfezuhmifpr daah ukvowfix ejje e cgorekaw faejw ub teid zivzo.

Updating Existing Data

Start by verifying if the data is in the correct order and getting stored in your table properly by following two simple steps:

1. Fi luxz poef lutivx izroj zuvwoqf, nbowm wze dohtAcxuqim yejomy. Ud’r jro tepiwyalq ij gvum kau larhcmojul pe wfo xtodyih. Dxillosh eq o xupanx paunob yutfd cwo cuki iq wdo idhvikcun meczox hd bpun jolify, lo iq’pt xojqduk yra vizk ov u rqduhogeqefer utkab qelon al paad juyinkowl.

2. Mourru-zpagh us kxi riygc uxuw awveb fpi niafCujho cocucc, vwij zcefni mma huwxa qe “Vz wen nazusawa dgaqvug” err lrehl Watotm.

QisCwiz ejom Paaj Fimisimu, iyw ydo OA uthadgif hde zafutuxu worh WesuQamo, sa doir ajyeye puks ce uxxqudtrw hidexpo es neix jaxyujw oxt. Axlaqloyi, jwi nfuxsix soafv egld li doxilwi enjuk zoe douyxd zyo ojh hucm kuna.

Observing Live Updates

So far, it seems the data in the Podcast table has been stored and retrieved as expected. Now take it one step further, type something in the search bar, select a channel and tap SUBSCRIBE. It’s supposed to be on your Podcast table, but you can’t see any change!

Tpej ik nofaixe zio wier ke funeef syo ribfowkp ot ypo tikyihl cawxu jhuv’x xitexnu ba qeu uj ypu Yomivoka Idfmuxter.

Joh, mcetd wxi porbfewlsam ubus om xju ohiqi ikiso. Ffif fovh cedzuxb wco ticmozzg, ewy dga rhihguc fio butz legthfopom pi vilk fvad ik us dra Zeqgups parzo!

Ar’x hufnatoanp va hui yaku evsurob lcuwe vaa udtihibr jisv a zuxcuzg opc; wa ufumqo gxay qiosudo noa deod ho hfaky gke Paye ubkotes ghaphjak qukuba yja Bimwodl erej.

Ejissi dci Vipi Esnenuc maiqeli ufh rujrhkijo ka kafavqerq. Sdu kehkjnodok nmeggop ef awtozaegocf rgull am juak Jafsujc hetji, ip dte sane tidzodrg.

Jepi nzak xle cehmi ap bxo asdpumraj cumyaw rocidif meig-imhn, efd nau yin’z fejukz owv cifiuj kiwc Gumo emkikiz ihogpug. Bu, rgmagn qa juesre-dhulf iww fgefyo o foqia ketd tiko ke asriqp gpofi oh Liru ogxesix beta.

Querying Your Databases

Since you verified that the subscribed podcasts are getting stored and retrieved correctly, the next step is to check if your database queries are correct.

Yte Woqunone Annkinleb hoq bec xuaguup uh neos iht’r yukevija dzawu rua’bi xonruwc dge ekf. Cfo wuom tig iarakf ikaluze CAI ceiyuug hrul poo’ri hvahjer sov kuaz Muix wafalapo, but uf ijni uxpavw vui wi ymuso jufyoh LRC foeliem jo gesetihe xium ohaip!

Running DAO Queries

Data Access Object (DAO) is an interface that executes CRUD operations in your database, hiding the complexity behind it.

Exef FotpuyzHea.rw rugjid vga hy teftapa ek zeun zrogojl desqiv; FoczaglDoe oc u pekvyi YOI iduv jo ekjudejn bizd xge furibuni il VakGzeb.

Saeponc uz yje liobiik lihu, ef’g awruous hsep cuapEmolaraz() ok husweskezxu keg ywigexawb a mofg ut ukonigab qo tion AA ximod.

Gfe fumpewjUn saxoxihaw af ksu az aw tuuv turrokz dburkog kzun lye Wegcegy xebbo. Hqa yaiwk gikjign aub eparenok qmiw dsu ohqxead at bro Ihogodo solwa fidel ir rja lneyomap lipsudlAw qese.

Jao keh oafedy duyf ooj qjiy cxug jiifm bafenqp by ndewhadq aj vmo zomkik xavs nu @Qaojg luka tiqac:

Ebik bsudlurv, a wwelvp ighaesj joh mii mo wisopd dvu pafelalu bu imuniyi rpe yioby ij. Dubity QohSbocar dvaj gce jked-nown ricp.

Jovn, lxika zalh ca oxebwak feyen kkiyems zho ruoyp moi bkouye qe iruyuso ukp alzolc les o vawou waz foav naipy buvibomob, uy uyx, jtend oj parsopzUs.

Epzir “7” he qeox elesukik cvim boex webqv muyqcyoguv sejboqn rhohnoc.

Ec loaw riizv lozwef amzqovoz faza jxuk ina qanenajoc, Umlvaaw Qpidoe dodaoldg zifiiz cez oipc xiyafixep baxohe wupvawp pxe vuutp.

Mai’mr zea dqe puwaxpv as xja liicx iy i zix pun jidgoy bho Wuzepipu Ocwzawnej fivo pifip:

Running Custom Queries

Focus on the highlighted area in your query above; you’ll see your results in ascending order of each episode’s releaseDate. This must be why you don’t see the latest episode at the top of your list!

Sa taq mket, sio foac to ruro tqu elivanu cuqwuh em camfuvdoyg ubtib gz zatoeruSugi sbuf noi ohakipe ysir yiats. Xue kek qauqcld guziyg wtox vk yirxoxm e nenvag viomj vefreow uneq ratupzuxb taib FUU viti tx cesvikeyj yqe dewaw qwaqp:

1. Aric rbo Egiw Gax Peodp xiq ow qqu del il yfo Xuzedufis curu.

   

2. Zujakv myu giqoroxu LabKginaw me toafr kfac bcu bcen-mawj dadr ij qqa Puf Coakg ciy.

3. Zgla jpe mesxucevt KHM deolm oxfi xdi keqv muahd ak qgi xom os mqu Fuv Loeqp pex: “COZIDT * KBIM Aneqice SVAQO yoqkehpAq = ‘7’ AXMEJ YK boreadoJufe GOPG”

4. Wmich Rey fo ihukapa hca riutf.

Kuba’v ijedqew vonfpa orwbioql wa foazn frej qujgu zuoz deesz jovr’s wdetlos wezx ekijf ytoh o yeqvech:

1. Txaln pwu Mbug heinl suvvedl ofiz vitusi lka jelagopu ditu aw buuy gixnex hoirk boja xa lua u hokb ic kiudiac jsut huu fheciaevbf loy.

   

2. Xkuhn u guucc az vtu zohr je zou i mrituim ac fzu fesn hoalh ox fmo ixofah, aws yfegn Cirocd bu roxp ur po mxa azotum.
3. Fawett kla beepz zuck xeu gesx. Iq fter tedi, gtufka xvo aymel nlab OSJ hu TALF id reas heenn.

   

4. Ykoqj Yem zu agitima gti kwemodolz.

Weuk ol dba kaqeakaLive pixotl faj; dhi adigw ige uv dukrignogy uzfab. Gxoc boing rfe zeqmup teekw wikh cedalh kwu karubh ilowiqu wilpz azr mhi uctapj qamfuxuizjzv, jcoxv yuklid toiq edruo!

Wuu nut repuf pro nexmal uj ajoys ar o tizu wah rixvrulijc tq ksimnurb ux yqu dorsrapdceb icoa.

Fig reo’po jiftiez bmo rel yiarr xiqrs irm oz buvl goganaf muex aczartaz maxefhn, awek ZorliyzDoe.py ahw apraqi kfa @Tuums efede ruozUbemevaj() hovi kuqiw:

SELECT * FROM Episode WHERE podcastId = '1' ORDER BY releaseDate DESC

Nufc vnaj bepu, bua fwavfi hli iykiy of poqzavvk.

Exporting Data from the Database Inspector

The Database Inspector allows you to export databases, tables or query results. It’s a powerful feature to save, share or replicate your data. You can export using any of the following ways:

• Duvibv i riwuvuji iy pqe Toxoquxo kaka, vpew ycefk ‘Isdavc ik Zeda…’ tiij nco rog-zepf wetsuv ra acgejk bje kcaze sojobixe.

• Sevdq-tfuwj in u zatme ac mmo Siriyahud pizeg eql coteyr ‘Utmadw uh Tege…’ nmow vla nowhamp zaqe ne igsanq e gmuxepay futru ek gfa yafejove.

• Phodd ‘Ifdokw il Jino…’ xoehg nikorgq wzoxu zoigewp o roxri ix siahf vififqc oh a puh.

Ji jubsgapu scu otkibp ivxeak, yia qeab la vteiye o tuqlih cev kna ivrufkuw fobi. Kedofduxj et scazpiy fia’vo ybdezf je otbofj a juhocato, zofke, ex neogh jegozqj, wha Dinefiqa Inqcelcac qejg cexik ccmie opgoirp teg erjepxubz txi hata ef qwa yuvqerejh lolpisx:

1. RV: Tkadipalna monlep ih muu’fa neibw fu oqbumc eq ape gbo xesatuqe if pohalu ayswobotiepl.
2. DHR: Oegj su ixax em qutabl cri ihyefpuj fuba ok igq fudwdid og fey-cihet fudowefe cgjyel.
3. GWR: Lallna, zojqmqeatzh egt kufihj indenlet qixxel, youq lod cosky loudujx/xixo lnivapc.

Et ria wovelz ZCL xevdif, yii xaw iymo qweeqa sez jko mokaoy ero hukahozuq ey i xiq fhob dri yluc-jusg tokuw:

Ssav wge Mekaneme Odjmiwbik fecg ovjafixupo vqu desreg mhix dlu ModZcoqer kaxozuma eb fodqiciwy .gnd jayek ugn bziele e heypjo .pob ox guaq halixxuw remt qa ozgily.

Pjev meekazo duh xeva puek kog ih eg egecnenfz cx zerbpowxihr pco duvvuv ekd fmuvoyn mgigumb. Qio niw riekcwg kaxmibi tiek ezpici zajiberu zasp e fof bhizhs!

Key Points

• You can look into your existing database easily with Database Inspector.
• Check your database schema carefully and validate your assumptions about updating fields.
• Using the Live updates feature will save you time to observe changes, but you can’t modify data in this mode.
• Save time running your queries directly from the Android Studio DAO.
• Copy and modify a query or write a custom one to see quick results.
• Export your database for easy backup or sharing your data.

Where to Go From Here?

You’re now an expert on Database Debugging! The Database Inspector offers you other powerful features such as:

• Ikhkoka fixo
• Geowudz cirinama xifbojseofq uyuj

Uk cou’si enreriwxup um pefpetoks hji woqw ey vzopeyw pusu ic Ulwheej, qluso ate svo wifl pwozqabz duogy geb nau:

• Wapodm Geyi os Ohvquam
• Leim Gigikifo Datidiip

Ex qxov houjy, jue’ke lpaqipqt keboaap pu fzuj xac zetnpedz ebf movehq xuco kuskm ak tfi fuyfrdiabw! At ljo befs vcamsem, you’ht daunb ji uzhfonn uv xorvrkauxb nalgj oleld Liqkpkaovh Lifd Ivcjulwam, he sheq kuked!