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https://github.com/ent/ent.git
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73e294a21e
Summary: Pull Request resolved: https://github.com/facebookincubator/ent/pull/154 Loading the "form" table is not required where there's no predicate on the join. Reviewed By: alexsn Differential Revision: D18421062 fbshipit-source-id: cb2a045a5a8a76ea4f07e5cf4305a6da338a616e
105 lines
2.8 KiB
Go
105 lines
2.8 KiB
Go
// Copyright 2019-present Facebook Inc. All rights reserved.
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// This source code is licensed under the Apache 2.0 license found
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// in the LICENSE file in the root directory of this source tree.
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package sql
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// Rel is a relation type of an edge.
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type Rel int
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// Relation types.
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const (
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Unk Rel = iota // Unknown.
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O2O // One to one / has one.
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O2M // One to many / has many.
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M2O // Many to one (inverse perspective for O2M).
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M2M // Many to many.
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)
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// String returns the relation name.
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func (r Rel) String() (s string) {
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switch r {
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case O2O:
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s = "O2O"
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case O2M:
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s = "O2M"
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case M2O:
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s = "M2O"
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case M2M:
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s = "M2M"
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default:
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s = "Unknown"
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}
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return s
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}
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// A Step provides a path-step information to the traversal functions.
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type Step struct {
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// From is the source of the step.
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From struct {
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// V can be either one vertex or set of vertices.
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// It can be a pre-processed step (sql.Query) or a simple Go type (integer or string).
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V interface{}
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// Table holds the table name of V (from).
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Table string
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// Column to join with. Usually the "id" column.
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Column string
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}
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// Edge holds the edge information for getting the neighbors.
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Edge struct {
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// Rel of the edge.
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Rel Rel
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// Table name of where this edge columns reside.
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Table string
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// Columns of the edge.
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// In O2O and M2O, it holds the foreign-key column. Hence, len == 1.
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// In M2M, it holds the primary-key columns of the join table. Hence, len == 2.
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Columns []string
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// Inverse indicates if the edge is an inverse edge.
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Inverse bool
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}
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// To is the dest of the path (the neighbors).
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To struct {
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// Table holds the table name of the neighbors (to).
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Table string
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// Column to join with. Usually the "id" column.
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Column string
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}
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}
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// Neighbors returns a Selector for evaluating the path-step
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// and getting the neighbors of one or more vertices.
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func Neighbors(dialect string, s *Step) (q *Selector) {
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builder := Dialect(dialect)
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switch r := s.Edge.Rel; {
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case r == M2M:
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pk1, pk2 := s.Edge.Columns[1], s.Edge.Columns[0]
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if s.Edge.Inverse {
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pk1, pk2 = pk2, pk1
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}
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to := builder.Table(s.To.Table)
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join := builder.Table(s.Edge.Table)
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match := builder.Select(join.C(pk1)).
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From(join).
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Where(EQ(join.C(pk2), s.From.V))
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q = builder.Select().
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From(to).
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Join(match).
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On(to.C(s.To.Column), match.C(pk1))
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case r == M2O || (r == O2O && s.Edge.Inverse):
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t1 := builder.Table(s.To.Table)
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t2 := builder.Select(s.Edge.Columns[0]).
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From(builder.Table(s.Edge.Table)).
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Where(EQ(s.From.Column, s.From.V))
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q = builder.Select().
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From(t1).
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Join(t2).
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On(t1.C(s.From.Column), t2.C(s.Edge.Columns[0]))
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case r == O2M || (r == O2O && !s.Edge.Inverse):
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q = builder.Select().
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From(builder.Table(s.To.Table)).
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Where(EQ(s.Edge.Columns[0], s.From.V))
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}
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return q
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}
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