Pratique du Shadowing: what is a database index? - Apprendre l'anglais à l'oral avec la vidéo
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68 phrases
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we really need to talk about what do we mean by
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an index very quick we added this concept of indexes
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because of a problem
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that we have in database systems you see we have regardless
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of the way you store your data whether it's a relational table of columns and rows or documents or blob storage
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this data is huge in your table you're going to have millions
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and millions of rows in your documents you're going to have thousands
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and thousands of documents in your blob stores you're going to
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have these content these blob pictures videos whatever contiguous one of the other
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but searching becomes interesting
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because how do you find something in this pile of stuff you get a scan one by one
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these million rows or thousands of document or tens
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and thousands of these blob images which is obviously not ideal
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because you have to loop one by one
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and you have to visit apparently work with millions of rows to find what you're looking for
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so so smart people found a way to eliminate working with millions of millions of rows
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and instead work with as few
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or rows as possible to find exactly what we're looking for
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the the best solution to search billions of rows is to
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avoid searching billions of rows right that's that's the best solution
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so the trick here is to take shortcuts so indexes was well born
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and there are many many types of indexes
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that helps you you know find exactly what you're looking for
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or at least narrow the search not exactly gives you one io or one cost bigger of one not necessarily
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but it helps you you know narrow
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that search that's the goal of an index
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so regardless of the type of it is a b3 b
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plus tree you know uh jest tree generalized search tree
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or brand the goal is just let me work with as let me eliminate things
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that is absolutely doesn't contain my results right just like concept of a bloom filter
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so that's an index so i have an index
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and you search this index so you still need to search
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but it's a much much much smaller data structure compared to the millions of rows
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that you have on your actual data blob store documents right
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usually you keep we call this area the heap right the heap is a data structure where you just dump everything
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ram it's just a dumping ground index is an optimized data structure
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that helps you pick what column in your document
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or on your row on your table and exactly index
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that column and the goal is to give you give you a row sets right a sets of rows
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that are candidate
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that may give you the results after you search the index
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you get a list of candidate results right could be one
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or could be more you still in most situations you still
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need to go to jump to the heap to the big table
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which contains actual data and fetch the content
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because the index will only have one column
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or two right the heap will have everything in it
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so you jump back but the index tells you exactly where to jump
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and that is the trick here the index tells you hey jump to page 179
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and pull row 73 in that page it tells you exactly
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that right now it depends on the database the database is
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sometimes does an additional filtering upon fetching the row itself
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because there are situations where the row might have been deleted
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but the index wasn't updated and and we need to see
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if i'm supposed to see this row or not
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so whether whether you're in a multi-version currency control or not so this is an index Cool.
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Sounds like a good data structure, right?
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Beautiful.
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Let's always add an index.
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Why not?
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But careful with that.
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What did we say?
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We said that the index gives you a candidate rows so
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that you go to the table and fetch exactly what you want.
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Right?
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Cool.
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Keep that in mind.
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Okay.
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Vocabulaire et conseils d’expression pour cette leçon
Cette vidéo contient 68 phrases et 696 mots à répéter en shadowing. La partie parlée dure 5:12. Le locuteur parle à un rythme régulier d’environ 134 mots par minute, confortable pour le shadowing. 87 % des mots font partie des 3 000 mots les plus courants en anglais, le vocabulaire est donc facile à suivre.
Vocabulaire clé de cette vidéo
15 mots moins courants de la vidéo, avec leur prononciation et leur sens :
- column /ˈkɒləm/ (nom) — colonne. A solid upright structure designed usually to support a larger structure above it, such as a roof or horizontal beam, but sometimes for decoration.
- database /ˈdeɪtəˌbeɪs/ (nom) — base de données, banque de données. A collection of (usually) organized information in a regular structure, usually but not necessarily in a machine-readable format accessible by a computer.
- fetch /fɛt͡ʃ/ (verbe) — ramener, rapporter. To retrieve; to bear towards; to go and get.
- regardless /ɹɪˈɡɑɹd.lɪs/ (adverbe) — malgré tout, malgré cela. Without attention to warnings or indications of bad consequences.
- trick /ˈtɹɪk/ (nom) — tour. Something designed to fool, dupe, outsmart, mislead or swindle.
- narrow /ˈnæɹəʊ/ (adjectif) — étroit. Having a small width; not wide; having opposite edges or sides that are close, especially by comparison to length or depth.
- filter /ˈfɪltɚ/ (nom) — filtre. A device which separates a suspended, dissolved, or particulate matter from a fluid, solution, or other substance; any device that separates one substance from…
- eliminate /ɪˈlɪm.ɪ.neɪt/ (verbe) — éliminer. To completely remove, get rid of, put an end to.
- dump /dʌmp/ (verbe) — se débarrasser de. To release, especially in large quantities and chaotic manner.
- necessarily /ˌnɛs.əˈsɛɹ.ə.li/ (adverbe) — absolument, nécessairement. Inevitably; of necessity.
- compare /kəmˈpɛɚ/ (verbe) — comparer. To assess the similarities and differences between two or more things [“to compare X with Y”]. Having made the comparison of X with Y, one might have found it…
- ideal /aɪˈdi(ə)l/ (adjectif) — idéal. Pertaining to ideas, or to a given idea.
- currency /ˈkʌɹ.ən.si/ (nom) — monnaie, devise. Money or other items used to facilitate transactions.
- loop /luːp/ (nom) — boucle. A length of thread, line or rope that is doubled over to make an opening.
- delete /dɪˈliːt/ (verbe) — supprimer. To remove, get rid of or erase, especially written or printed material, or data on a computer or other device.
Les verbes à particule que vous entendrez
- look for (verbe) — chercher, rechercher. To seek.
Prononciation à surveiller
Le locuteur utilise 10 contractions et formes réduites, comme you're, doesn't, I'm. Prononcez-les sous leur forme courte, telles que vous les entendez.
- Mots longs — placez bien l’accent: eliminate /ɪˈlɪm.ɪ.neɪt/, necessarily /ˌnɛs.əˈsɛɹ.ə.li/, contiguous /kənˈtɪɡ.ju.əs/, generalize /ˈd͡ʒɛn.(ə.)ɹə.laɪz/
Comment s’entraîner avec cette vidéo
- Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
- Répétez phrase par phrase à vitesse normale, en reprenant chacune jusqu’à ce que votre rythme corresponde à celui du locuteur.
- Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme column, database, fetch.
Qu'est-ce que la technique du Shadowing ?
Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.