end
c45e8abe08
Add transport-neutral keyset pagination through native Bob query mods. Preserve supported cursor value types in a compact versioned format, with bidirectional pages, explicit row keys, and a separate opt-in count. Include SQLite tests, PostgreSQL service CI, and the cursor-format ADR. Closes #6
69 lines
2.2 KiB
Go
69 lines
2.2 KiB
Go
package page
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import (
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"context"
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"fmt"
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"github.com/stephenafamo/bob"
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"github.com/stephenafamo/bob/clause"
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"github.com/stephenafamo/bob/expr"
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"github.com/stephenafamo/scan"
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)
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// Mod applies validated keyset WHERE, ORDER BY and integer LIMIT size+1 to native
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// PostgreSQL, SQLite or MySQL selects. Apply once to a query with no existing
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// ORDER BY, LIMIT, OFFSET or FETCH; do not override pagination afterward.
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// Callers may compose additional WHERE filters before or after this mod.
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func Mod[Q interface {
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AppendWhere(...any)
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AppendOrder(bob.Expression)
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SetLimit(any)
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}, T any](p *Prepared[T]) bob.Mod[Q] {
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return bob.ModFunc[Q](func(q Q) {
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var alternatives []bob.Expression
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for i, c := range p.sort.Columns {
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desc := c.Direction == Desc
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if p.direction == Backward {
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desc = !desc
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}
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direction, operator := "ASC", ">"
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if desc {
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direction, operator = "DESC", "<"
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}
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q.AppendOrder(clause.OrderDef{Expression: c.Expression, Direction: direction})
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if len(p.anchor) == 0 {
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continue
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}
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terms := make([]bob.Expression, 0, i+1)
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for j := 0; j < i; j++ {
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terms = append(terms, expr.OP("=", p.sort.Columns[j].Expression, expr.Arg(p.anchor[j])))
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}
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terms = append(terms, expr.OP(operator, c.Expression, expr.Arg(p.anchor[i])))
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alternatives = append(alternatives, grouped(terms, " AND "))
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}
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// authz: group the seek disjunction so caller filters constrain every branch.
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if len(alternatives) > 0 {
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q.AppendWhere(grouped(alternatives, " OR "))
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}
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q.SetLimit(p.size + 1)
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})
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}
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func grouped(expressions []bob.Expression, separator string) bob.Expression {
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return expr.Join{Exprs: []bob.Expression{
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expr.Raw("("), expr.Join{Exprs: expressions, Sep: separator}, expr.Raw(")"),
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}, Sep: expr.NoSep}
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}
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// Count executes a separate caller-built, authorized count query returning one
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// int64 column. It never rewrites a paginated query or infers grouped/distinct
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// semantics. Nothing runs unless called.
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func Count(ctx context.Context, executor bob.Executor, query bob.Query) (int64, error) {
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// authz: callers supply the same authorized relation as their item query.
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count, err := bob.One(ctx, executor, query, scan.SingleColumnMapper[int64])
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if err != nil {
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return 0, fmt.Errorf("page: count: %w", err)
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}
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return count, nil
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}
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