Iteratorでページネーションを実現する

Transcript

1.  1 *UFSBUPSͰϖʔδωʔγϣϯΛ࣮ݱ͢Δ (PͷΠςϨʔλਂງΓ/JHIU
   !TPOBUBSE
   ͦͳଠ
   גࣜձࣾ4UBDL
2. 2 *UFSBUPSͷ࢖͍ॴ w NBQ
   fi MUFSʜTMJDFपΓͰ࢖͑ͦ͏
   w ˠͳΜͱͳ͘Θ͔Δ
   w ଞʹ͸ʁ
3. 3 %#ͷϖʔδωʔγϣϯΛߟ͑ͯΈΔ w TQBOOFSD
   QBDLBHFͰ$MPVE
   4QBOOFSͷૢ࡞Λϥοϓ͍ͯ͠Δ
   w ҎԼ͸*UFSBUPSΛ࢖͏લͷίʔυ cursorInfo = offset.NewCursorInfo() for { stmt := statement.ByCursor[domain.User](cursorInfo) users, pageInfo, err := spannerc.GetMulti(ctx, stmt) if err != nil { return nil, nil, fmt.Errorf(": %w", err) } // usersʹԿ͔͠Βͷॲཧ if !pageInfo.HasNextPage { break } cursorInfo.Cursor = pageInfo.EndCursor }
4. 4 cursorInfo := offset.NewCursorInfo() for { stmt := statement.ByCursor[domain.User](cursorInfo) users, pageInfo, err := spannerc.GetMulti(ctx, stmt) if err != nil { return nil, nil, fmt.Errorf(": %w", err) } // usersʹԿ͔͠Βͷॲཧ if !pageInfo.HasNextPage { break } cursorInfo.Cursor = pageInfo.EndCursor } ࣍ͷϖʔδ͕ͳ͚Ε͹GPS͔Βൈ͚Δ ࣍ͷϖʔδͷ$VSTPSΛߋ৽͢Δ
5. 5 cursorInfo := offset.NewCursorInfo() for { stmt := statement.ByCursor[domain.User](cursorInfo) users, pageInfo, err := spannerc.GetMulti(ctx, stmt) if err != nil { return nil, nil, fmt.Errorf(": %w", err) } // usersʹԿ͔͠Βͷॲཧ if !pageInfo.HasNextPage { break } cursorInfo.Cursor = pageInfo.EndCursor } CSFBLΛ๨ΕͨΓɺ৚݅Λؒҧ͑Δ
6. 6 cursorInfo := offset.NewCursorInfo() for { stmt := statement.ByCursor[domain.User](cursorInfo) users, pageInfo, err := spannerc.GetMulti(ctx, stmt) if err != nil { return nil, nil, fmt.Errorf(": %w", err) } // usersʹԿ͔͠Βͷॲཧ if !pageInfo.HasNextPage { break } // cursorInfo.Cursor = pageInfo.EndCursor } $VSTPSͷߋ৽Λ๨ΕΔ
7. 7 cursorInfo := offset.NewCursorInfo() for { stmt := statement.ByCursor[domain.User](cursorInfo) users, pageInfo, err := spannerc.GetMulti(ctx, stmt) if err != nil { return nil, nil, fmt.Errorf(": %w", err) } // usersʹԿ͔͠Βͷॲཧ if users.Invalid() { continue } if !pageInfo.HasNextPage { break } cursorInfo.Cursor = pageInfo.EndCursor } $VSTPSͷߋ৽Λ๨ΕͯDPOUJOVF
8. 8 cursorInfo := offset.NewCursorInfo() for { stmt := statement.ByCursor[domain.User](cursorInfo) users, pageInfo, err := spannerc.GetMulti(ctx, stmt) if err != nil { return nil, nil, fmt.Errorf(": %w", err) } // usersʹԿ͔͠Βͷॲཧ if users.Invalid() { continue } if !pageInfo.HasNextPage { break } cursorInfo.Cursor = pageInfo.EndCursor } ࠓ·Ͱ͸ՄೳͳൣғͰ-JOUͰରԠ͍ͯͨ͠
9. 9 stmt := statement.ByCursor[domain.User](offset.NewCursorInfo()) for users, err := range spannerc.GetMultiIter(ctx, stmt) { var users domain.Users if err != nil { return nil, nil, fmt.Errorf(": %w", err) } // usersʹԿ͔͠Βͷॲཧ if users.Invalid() { continue } } ϧʔϓͷϖʔδωʔγϣϯॲཧ΍ऴྃ৚݅
   (FU.VMUJ*UFSʹӅṭ͞Ε͍ͯΔ 6TFSʹؔ࿈͢ΔॲཧͷΈΛॻ͚͹Α͘ͳͬͨ
10. 10 func GetMultiIter[T any](ctx context.Context, stmt offset.StatementWithCursor[T]) iter.Seq2[[]*T, error] { return func(yield func([]*T, error) bool) { for { stmt.Statement.Params["offset"] = stmt.CursorInfo.Offset() ts, pageInfo, err := GetMulti[T](ctx, stmt) if !yield(ts, err) { return } if err != nil { return } if !pageInfo.HasNextPage { break } stmt.CursorInfo.Cursor = pageInfo.EndCursor } } } (FU.VMUJ*UFSͷ࣮૷
11. 11 for users, err := range statement.ByCursor[domain.User](offset.NewCursorInfo()).All(ctx) { var users domain.Users if err != nil { return nil, nil, fmt.Errorf(": %w", err) } // usersʹԿ͔͠Βͷॲཧ if users.Invalid() { continue } } ͓·͚
    ͜Μͳ࣮૷ʹͨ͠ΒΑΓ(Pͷ*UFSBUPSΒ͍͠
12. 12 *UFSBUPSͷ࢖͍ॴ w ·ͱΊ
    w ϧʔϓΛந৅Խ͢Δ༻్Ͱ࢖͑Δ
    w 'PSͷதͰ͋Δ৚݅ͰCSFBL΍DPOUJOVFΛ͍ͯ͠ΔͷͰ͋Ε͹γϯϓϧʹͰ͖Δ
    w Ͳ͜·Ͱ*UFSBUPSʹ͍ͯ͘͠ʁ
    w *UFSBUPS͸௚ײతʹಡΈͮΒ͍ͷͰɺͪΐͬͱͨ͜͠ͱͰ*UFSBUPSΛ࢖͍͗͢Δͱٯʹ ίʔυ͕ಡΈͮΒ͘ͳΔ͔΋
    w ϧʔϓʹ໌֬ͳ՝୊͕͋Δɺ৑௕ͳॲཧΛ͍ͭ΋࣮૷͠ͳ͚Ε͹ͳΒͳ͍৔߹ͳͲɺ ༻๏༻ྔΛकͬͯਖ਼͓͘͠࢖͍͍ͩ͘͞ɻ
13. 13 *UFSBUPSͷ࢖͍ॴ w ͓·͚
    w %BUBCBTFपลͰ͸EBUBCBTFTRM
    QBDLBHFͳͲͰJP&0'ͳͲͷϋϯυϦϯά΋*UFSBUPS ͰෆཁʹͰ͖Δ
    w JP3FBEFSͳͲ΋ಉ༷ʁ
    w ͔͠͠JP
    QBDLBHFͷΠϯλʔϑΣʔε͕มΘΔͷ͸؆୯Ͱ͸ͳͦ͞͏
    w ࠓޙඪ४ϥΠϒϥϦ͕ͲͷΑ͏ʹ*UFSBUPSʹରԠ͍͔ͯ͘͠΋ཁ஫໨