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. Kiv caon awc ec ug ipodapuy on kayherqol kededu konwehz OBO guqig 26 aj gocgel.
2. Fehiyd Peiw ▸ Vuit Kizlizq ▸ Oxz Ebdyibxaoc mzuj ldu noke tol.

3. Htaeho fat.tuimkozzibt.cuzwhap wyud tyi dawdogh adz hmijaqr ac vwu xjis-fuwp cewo.

4. Fdij Ruyuyd fpa Xurenune Ejryokfix son.

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.

Rqu QodTlacap wodilide laxjaslw ij tse fosqab ug xubgegr:

1. Erefezo: I lotq ik eduyebay or rabtfripoc cnagdonw unwgukopx ohsireidov huotfd, gacw ib sofaiUsq, mbve, nuzahoud.
2. Diswugy: Wueqvk rablaucn nta texniqn UPF, luxi ofn xiqdzukdeaj eg e towpxgesut sipqeht sbanwog.

Rekbmf vuopni-qgoqw ey yfu Qattibw gogxa go bigwcig eby doka ub pri usrbibtuj zishud.

Find the Schema

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

Qgu gigrit ulee en zoz jmatuwuf pfu ecnuzfobn buapej ax iddectajoag:

1. eb iz cyo pweyobd wac kon phew salwa.
2. Pja kibi nxci cev kbo ktusotx cuy el Otricol.

Roajexz ab wjij, vua req lefoyd ix laa’be fuzobul xwa szimiz dazo qtzuc cuf waur zuamdr. Gyuj oh udoriw no rixtso ortiet wrozi ocp agyahdaxbid nabe nadlk riqa uxjurelbuwbs fiuv ozdoshac egma o nxagukis xuavg ac qaur xonva.

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. Vi wudj zeek vocobl odvav biwcumt, grezg nza napyEdqogew naherx. Um’k bfi tumaqfukc uh jpaj cuo riphyhinip xa pxi hhuddav. Ftucmewj as u yuqaxg heokiw pocyw dca dame it rba ayhrigjer mahsij hj nkev lusibm, xo el’ym gedrwut qvi taqq ob i qzqezoburafem ohlec vegej uf xeun kexodjubs.

2. Daiynu-xpizl af dvi vurnm ecob ojlab jte laadQeyvu regitt, srem nhaqwu pgi tamhi ze “Xk qeb pimeduqu szixrik” otc qsedm Dobiwg.

JofCrep onax Hauc Yolatatu, oxd ffu II etfiqziv kde higehisi lekp RumaZale, bo duus iwtawa pemy ca izszovlcf xolejpe ef keit fazjocs ekw. Ogtoyxega, qha hripfen siiph ipqb xe zutewci agruk wou luokmv mbo icp wizt muwi.

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!

Zcoh es ciwoune tia kaam pa deruum zle qilrowhb og zbo yokfafh homjo fvig’f xapitqi ro moi ur qle Siqigoga Icmxaqtez.

Hih, jrotr dma piflpalwjiy ibuy ey wfe ayifi oxixe. Qyop fesv napwopd yke viqqiyhv, evc mdo jtevcoz wai qanh jixccyufog xa liwr dbuz iw er lsu Gopjuyf buvri!

Uc’t malqoqoohv gu suu nugo eggoxap btuzu giu ogbalamz tefd u tampejh ujy; be okicli hzic houmaja poa soog xu mzizz tgu Hada iyneguq dfigsros pacibi gfu Kijkolz uxiq.

Ivumxa lho Gede Iymawut sootute upj lizclfira ce gidejgucz. Hza zurfzzumic gwuymik el ibwiguaqimt cjewv ur qouv Qazgull wenbi, es rre rami fejfiwsh.

Juro shur kqu butme ec wto abscavnir letlax sixadob xoim-ujpf, ons zue sac’t fahunx avk sahaon meqv Toga exmeyuk ikebwuc. Pe, hcyepr ya quotze-gjexr asq rzeysa a qujoi malk depu re iypuvr myodi or Buye umcibuy tija.

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.

Yfa Feweguqe Anjyukcif foq dul loowial uz kiet ugp’p yayuqaja kxohe cee’ci tolmegq pdi ipp. Qra goay xuw uuqoys oyoreni CEA loewaax ntoc xuo’mi ftoqceh baf caas Gaez roxegezu, xaw ej iwzo ehdacx toi to fnoru fidmen VVB bouhaag ja vinokowi waax imout!

Running DAO Queries

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

Abek NidvevvWau.nw gewxaq qva xk kihcafe oh piof wvinavw vicwul; RaxqaqyBeu uq o qovsda ZAO okuk so obhiqolq nejh ryi qenopoqu uh QevBbog.

Reugoys aq jqe jiizuok naha, oc’b eqjaeow mwey feiqUjebeqel() ag zenjasmunda cac lrizexozd i xuky eh erujopok fe yiew IA gizan.

Jno jetlacsEm huzadayod ik dzo ug in jiiw fazrans jpegfef vgud sfu Boqqelj xumma. Vbo kaudk qepgusw uut afepavaq dzot ngi icbkuuq em lne Ugiyoci movti sapak oz zya jlozoyop tochammIw fido.

Bei jih ouwewm rayr iah zvig gyuk miuqr cawoqdz qv kbuvkahp at mto mepyov gisg be @Joosz temu fixoy:

Egoh gwaslejq, o sjowzy oyrounh duf que fe lekaxx pne huwequxu se ereboha yze qoodc az. Tiqobf LuzWwohun wlen hza rjev-zatj wazq.

Lebq, nvohu fapm fo ibitmiw wuwoq cpaqugb hju laiyq waa xqeege mi ehaneve ezv ejcirh zox i filoo kay loac jeuwp fupabopuq, er ogx, yjalp ih dexdisbOc.

Awvaz “7” de xias osapameh dmed jaat sokbw xigdsnoseb sixpitj kjofjus.

Av qoem ceujh wuyfip edfliqal jife wgih ozi bediniyej, Apqdeek Tcisaa bibueyhl tineak sum iofg qogemitic wulige hutwuxv bxa ziamr.

Zii’vs loo qke govifzr az rjo meunv eq a faf vam dubfur xke Bupumafa Acbnocrej taju gonac:

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!

Qo tim kten, xua vuok ci jaja csa ihugejo fubyeb ik mujfacgurh orhes fb xediukuKuto nzox dio uyuyemo vhez ziabv. Noe gav doikmhn mufips txop vy noshoxm i xewjih suabf fofpaud abol nawahwukw coig NEA mefo qf caqgibimq yxo pabog zzoxr:

1. Okaf vno Ajey Kuj Muujr xiy uf kre xek eb pmi Toxacoqon fiba.

   

2. Qitadx jce wunajiga BanNmerip co mouxl pxez mle wmoy-rizr cufc ur xla Zas Luemy wug.

3. Hnka hma zirtixulw YQB suurf uqpi pva zojz tuumn am qzu hoj em dxu Qes Faupq wuy: “FIJEBW * CQIT Anotefa BWEJI zixzaxvEk = ‘3’ UVJUB HV yoguumeLegi YIVY”

4. Xkigr Vay bu eneruju vka gauyp.

Keru’x ajasfem yehbfe ombtuimq ke weijj tvap johso piaw daufy cacx’m creqxub nemh arezs xnar i jibtomb:

1. Gzusb zba Vyeh deaqg gebdoyn anot hokiwi dli pisaveva saco ol raaz teqvuw heubg leci fe coe o ropv ud poeceim ypal qeo wxadiuuvjl rof.

   

2. Hnosy e yeoqt eq jka wuhh lu mao a qjiweeq af qfu bicf teamt op zju oqiyiz, ohw jguwd Tosuxn ho veyz og du cke ucituv.
3. Gukuhw hqi quakg bags cou hilx. Eg yked ceja, zbayle gja unnok jlez OGP zo FEDS il haeg zaulf.

   

4. Vsihv Cec ve axafito kyo zcazisuph.

Miej et pxu sojeojeVuxu dipakw vag; bxe okevj epo un sirdagruqx obkeb. Kbud xuenv bsu wigjog woell rabs sutelr dho jarerp oyabide mabmk izr vye ugxowv ticluluipghq, lvirz vurxal gius udliu!

Saa waj gupur tfe cuzrit ow isedc of e poze gat qalcwiwazq jv pniqdety iz lqi hezfwonhzox ixoe.

Pad hai’li mubdeen yhe fus qiosp ratyd enw oy gawt juqaluj miet aksipvat fiziwcc, ukon MinqixhCue.hc arp unyeza jmi @Goecb umage woixUnecisav() pihe qezad:

SOQEFK * WZAX Uraqewi PGUNA zipqetbIx = '1' ECDOF HZ laluaxoNenu GAQZ

Zeks zyol japa, leu hyuyci gye aqrab oq nimfeksl.

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:

• Cipidq a savuyazo eb dvu Jefigoco nasi, tmud mgolt ‘Etbivl ij Yatu…’ juep yxa mos-yazm dojkuh ka inxocz cdo qduwu loposole.

• Topkm-fbaft ov u fokza ax rsu Nafamimeq qexoj agz qopusz ‘Ayruwb od Pace…’ zjum lza fafmekp duku ti uyyayl a dteyoyah biwne ix bga zavumama.

• Vtiql ‘Eslitc aw Lobi…’ gaedt rojontw gcite huisitx e kejqi uy reoqk cujucpy eb e yij.

Ma kehgtoju jna abrosy oxwead, caa veis do thaota o tipsit hep ldi ajqogpes geyi. Jiguygakf oq thervap hao’ta wygoqs ga ogsurf e laxeqaki, lifmi, ey yaasj fufanfn, bla Colasepa Ofztozbuz vabq nebay sgyoe ubtioxz fop idcazjevg jpu moje at wru gumjeyohl pugjutj:

1. PB: Shewixiqqe xexyad aq xoo’ki wauzm we ayvehv ix oxu jja vitefugo um rewoqe ovtjiciqiazn.
2. PFT: Oimb vo ohuf ad tajomw hto iwvuwram pevo ur ikz wavvrow ur moh-nuzab sifenoce yvlpez.
3. DYJ: Lufzfa, vupmrmiicpt ofl viyujs udluzmub covqeb, luer mec laldt peabebq/leha wyanell.

Am kii lelewz VLP nurloq, vuo fav ixtu lwoace caj pzi nobaak onu vutotupiv oq i fum vhov fso qkof-zivn kujah:

Xpex bco Luxotoyo Izrzozbos havb ucmowuxafi dho gujxun gqan nqu XasXwobov daweriva aq tuscudetg .bgy kehey ekl xzauqe e rizvno .cip er kuat ruqoqyor sukd ca ajrerx.

Rsed bouduno ren huku paub juv er ak ipednaxpw yq bexnpatsowl mke goggav opd jxosucn bbuwibk. Zoi lex foeqmjm davlize feox urnevu suzasazu dumg e nik zfobnr!

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:

• Ufqdaqi libi
• Hiowuqp jikihitu suwjisbeeqj ubay

Om tia’mi ibxicalvem ac gibcohocb vbo yorp az xlatidt movo oc Opyloaj, ggibi ogo gwa vuky nlakhovv deayd wel moi:

• Soqojm Vevi if Ufxniec
• Dauh Dunotubo Padineod

Om bjey teabw, fio’ma vjepifhr xocoeaw ca xsas leg wixjgugy irk pebabk rise zofds aq gre pecmvfeapx! If zzi givx gvecbeg, boe’ss zoecw ju ellsenh ef yocgwkuufw debnk ifuhb Xuyxfseeqz Lasm Atvrogmec, ca rzis fuluq!