Add eager loading for to_many

- Needs tests

templates/00_struct.tpl

@@ -11,7 +11,7 @@ type {{$modelName}} struct {
   {{end -}}
   {{- if .Table.IsJoinTable -}}
   {{- else}}
-  //Relationships *{{$modelName}}Relationships `boil:"-" json:"-" toml:"-" yaml:"-"`
+  Relationships *{{$modelName}}Relationships `boil:"-" json:"-" toml:"-" yaml:"-"`
   {{end -}}
 }
 

templates/relationship_to_many_eager.tpl

@@ -0,0 +1,78 @@
+{{- if .Table.IsJoinTable -}}
+{{- else}}
+{{- $dot := . -}}
+{{- range .Table.ToManyRelationships -}}
+{{- if .ForeignColumnUnique -}}
+  {{- template "relationship_to_one_eager_helper" (textsFromOneToOneRelationship $dot.PkgName $dot.Tables $dot.Table .) -}}
+{{- else -}}
+  {{- $rel := textsFromRelationship $dot.Tables $dot.Table . -}}
+  {{- $arg := printf "maybe%s" $rel.LocalTable.NameGo -}}
+  {{- $slice := printf "%sSlice" $rel.LocalTable.NameGo}}
+  {{- $pkeySlice := printf "%sPrimaryKeyColumns" ($dot.Table.Name | singular | camelCase)}}
+// Load{{$rel.Function.Name}} allows an eager lookup of values, cached into the
+// relationships structs of the objects.
+func (r *{{$rel.LocalTable.NameGo}}Relationships) Load{{$rel.Function.Name}}(e boil.Executor, singular bool, {{$arg}} interface{}) error {
+  var slice []*{{$rel.LocalTable.NameGo}}
+  var object *{{$rel.LocalTable.NameGo}}
+
+  count := 1
+  if singular {
+    object = {{$arg}}.(*{{$rel.LocalTable.NameGo}})
+  } else {
+    slice = {{$arg}}.({{$slice}})
+    count = len(slice)
+  }
+
+  query := fmt.Sprintf(
+    `select * from {{.ForeignTable}} where ({{$dot.Table.PKey.Columns | stringMap $dot.StringFuncs.quoteWrap | join ","}}) in (%s)`,
+    strmangle.Placeholders(count, 1, {{len $dot.Table.PKey.Columns}}),
+  )
+
+  args := make([]interface{}, count*{{len $dot.Table.PKey.Columns}})
+  if singular {
+    {{range $i, $col := $dot.Table.PKey.Columns -}}
+    args[{{$i}}] = object.{{$col | titleCase}}
+    {{end -}}
+  } else {
+    for i, obj := range slice {
+      {{range $i, $col := $dot.Table.PKey.Columns -}}
+      args[i*{{len $dot.Table.PKey.Columns}}+{{$i}}] = obj.{{$col | titleCase}}
+      {{end -}}
+    }
+  }
+
+  results, err := e.Query(query, args...)
+  if err != nil {
+    return errors.Wrap(err, "failed to eager load {{.ForeignTable}}")
+  }
+
+  var resultSlice []*{{$rel.ForeignTable.NameGo}}
+  if err = boil.Bind(results, &resultSlice); err != nil {
+    return errors.Wrap(err, "failed to bind eager loaded slice {{.ForeignTable}}")
+  }
+
+  if singular {
+    object.Relationships = &{{$rel.LocalTable.NameGo}}Relationships{
+      {{$rel.Function.Name}}: resultSlice,
+    }
+    return nil
+  }
+
+  for _, foreign := range resultSlice {
+    for _, local := range slice {
+      if local.{{$rel.Function.LocalAssignment}} == foreign.{{$rel.Function.ForeignAssignment}} {
+        if local.Relationships == nil {
+          local.Relationships = &{{$rel.LocalTable.NameGo}}Relationships{}
+        }
+        local.Relationships.{{$rel.Function.Name}} = append(local.Relationships.{{$rel.Function.Name}}, foreign)
+        break
+      }
+    }
+  }
+
+  return nil
+}
+
+{{end -}}{{/* if ForeignColumnUnique */}}
+{{- end -}}{{/* range tomany */}}
+{{- end -}}{{/* if isjointable */}}