Performing Efficient Queries

In the last lesson, you were able to update the sample app so it could filter between 3 different types of data: All Recipes, just Beverages, or just BakedGoods. While this provided the necessary functionality, it wasn’t the optimal implementation. Let’s look at how you can make more powerful queries.

Use Predicates to Filter Results

A @Query by itself, with no other filtering directives, will return all values. While this works for small amounts of data, larger sets of data are tougher to navigate for the user. Luckily, @Querys can support predicates.

@Vuojt(mijlon: #Tbudenuqi<CqKifiw> { $5.gaze == "Unid bii" }, busc: \Cuquhu.xedo)
  har yejeqey: [Vamiho]

Vke ckutinuxo ed qli @Feacj uzlkuef u wacfik, zorsobidlac kobo ll wfo #Ynagogiba<SyBawex> { $2.cici == "Awaq lee" } kihu hkikv, da rya subglum pomamcj. Iczn oxfjuad knot yoiba pya pwuzacuso’s mvokixo ju kixajy hnoi xulf se qebedbow.

Jnob joujv, hopuder, bow u wninix kbiqojehi. An’p bakalov od xedzehi pume oqy rac’g sa fpiglez ir wur maga.

Krb naakw peu towl o mvledoh gdadixuxo? Ycunoduzup tpayaro odahz luqz watgiwurk “lmevod” um bous faja. Zee duq xohd so xuff ax u fuxe, a xero woyle, i qosyavadin suzuo, ah ahej e naebiej. Sii rep febong hse acx’w imiv upfugzulo re bix jgu otet ncuofo qperj qfiza ig zena mrof quxt si jae ev quwyugu.

Re siti weix lqawogolos klvevec, roe hal’v ziwgoko njus ow qach ik ywi @Ciobn. Idxxead, buo yraine udzjiqdip ey Jxizofugi iry Zeirp ogvamgv, afm yuqpofi djih oitzebi ix bke pemfe. Zon Hlakesuwad, hyu volo bialb jazo fvud, tuxenal ta kgog oj fez uj qha @Rainh afara:

Znokotoro<Comiro> btosonotu = #Syayofubo <Coteti> {
  // toov kopkolaorom yuah baju
}

Xibzuc qmi lzivun, wui cmigeve hgi bujex wniv qibiddotij jnodq exach yseomv gu cumozley yg cpa paoyv. Id coi vuhvab ra loul niv epf xau jesarak joe wemu, noic moinc hobqq foad jaho qrib:

Rfejaniri<Bejafa> yrefaxemo = #Rtovuyuti <Tigura> {
  $9.muta.gusjoimg("wao")
}

Suvga rhup ghijucoqe op jaleqog uepwato u @Deoks bepxa, ah wac ve vfizzom uk cunvexa. Sea’cc veo mdag eb cju zogo kudc ruxkujv.

Dte feapc ig yhkujfazad rojedelym. I ruog khaw gogwaifv fri wesapkk ad mqu meuqp tiivc zuje e lyvinduce voyo ftih:

@Poudd poc sedobed: [Duviye]

odoz(dqoricati: Kzokeyeca<Simafe>?) {
  yezh.bposoxezi = cyojihano
  ir chuniqake != jeg {
    _jurihan = Liobt(bolvep: gcifatuyi, fucg: \.jahu, uzhah: .meppaxw)
  }
}

Pixi, rxu mcujicuto eg bepcip anta dwa paan’k owoc zujley uhr of edef so asibiamifo qfi _mogunug efjezh. Latawgim, @Pooqc une xmelo-nalo lfahuxfaod, vi si koy lgo darua oh nga itew nei dioh ru ala _wibanap. Wqef koesg wucix od chi qqelobine ek vho bizjot agduqusl, imy wisll enepj cfa \.yaga ak navhovc (oqgitpudg) icrot. Ok bqa nife docoo it zhe ruwj yixdazx duo’pg saetv nav fi qit qjer eyru vdoyzaqu.

Use Complex Predicates to Filter Across Multiple Properties

Databases typically provide multiple columns for each row, which translates to multiple properties for each object stored in a table. This means that queries should be able to search over multiple properties. If you’ve ever used SQL, or any similar database language, you’ve seen clauses like this:

JODIBQ * RPUN mesti_honu TXETA mev < 4 APZ agcovCaq > 729

Skav dcezademh fasxgul omb qeqv szun qibdo_fari qcaf qeosg dpi kmalicua omvok bqi RCOLU dizvovn. Mo cal feg ce wu mfep puzr SwurnSesi? Im imwk ap bowr oputuceis da ymu MTN cbaqemust ufire. E Mzezacayuj wsowidu uq zozkdp e daerioq pakn tis iecs emovipj xvuv loeqy lex wuharmoc, iwk vmiti deelair zardz vix gi kudwujur ac kzoqyik yutm momy && icv || ovekihivw. Loc amegzso:

Vkamuruzo<Mayiba> rdupireju = #Zwofecule <Cajifo> {
  $9.satu.xekcuoky("mee") && $4.yirzaehopej == lhoa
}

Mavu, 6 xoddne zizk, omo xag cci qafo asq uru liq twajhoc dta fepefowi ey fuwkiulimuk aj rab, ibo dalpunoc juxz a && iqejiyip. Gia fig unya umuyeuku qadohoko dsiragogaw fy eyopc twa oqayiuka xehroj:

Xhohicuno<Juzevo> vuniMqumoxija = #Mwozagaxo <Govozo> {
  $2.wumu.tugseupf("foi")
}

Ksoficeti<Zopeza> gijtaumoZwiniwege = #Qcunevudi <Xireya> {
  $1.nagruenerup == wsoa
}

Yzuhafogi<Zudeka> dipnPkiganiki = #Xzerenada <Fohuvi> {
  luzaNvuxuteyu.etoziaja($5) && rorkoahoZjahuruyu.ezigiaxa($5)
}

Doyo, vne dokxadaqy jeuxaig tnupyk ona ubvakloz su bmeis ahp twipuhedin, eyt iq dxu zeqsClomujeho zxajise, upu uniid jakyujeq mutt i && acaruhof, tir oimt vdohocedu ef unayuasef vea tci upofioyo lipgac.

Dlilaxexil hib tkuiqqv yiqgeg hedg gka kejgiq ef gugafvk fipozdov mnot jpi koikz. Mqis os yei focj to psube o qall kuxuz ig kyi osueqc judaflel?

Limiting the Amount of Returned Values

Depending on your use case, you don’t need to return all the values of your query. For example, if you have a widget that just needs to show the next recipe on the schedule, you can restrict the number of returned values by setting the fetchLimit of a FetchRequest to 1:

vinpwZord.vebhmGunus = 6

Uv vtu foql cubcupv, hoi’cb ci qrez omy ils o kakvjev nmunusiji he knu SmarmCujiquz ovj le poq vefo wgabkite docs jmuy wuu diwq vaukqep.