Add limit and offset to QueryBuilder, mild refactoring (#284)

* fix typo "include" => "extend"

* refactor builder assemblers

* add limit and offset

* add limit and offset spec

* remove SQLBuilder

spec/granite/query/assembler/postgresql_spec.cr

@@ -26,7 +26,7 @@ require "../spec_helper"
         query.raw_sql.should match ignore_whitespace sql
 
         assembler = query.assembler
-        assembler.build_where
+        assembler.where
         assembler.numbered_parameters.should eq ["bob", "23"]
       end
     end
@@ -41,5 +41,24 @@ require "../spec_helper"
         builder.order(id: :asc).raw_sql.should match ignore_whitespace sql
       end
     end
+
+    context "offset" do
+      it "adds offset for select query" do
+        sql = "select #{query_fields} from table order by id desc offset 8"
+        builder.offset(8).raw_sql.should match ignore_whitespace sql
+      end
+
+      it "adds offset for first query" do
+        sql = "select #{query_fields} from table order by id desc limit 1 offset 3"
+        builder.offset(3).assembler.first.raw_sql.should match ignore_whitespace sql
+      end
+    end
+
+    context "limit" do
+      it "adds limit for select query" do
+        sql = "select #{query_fields} from table order by id desc limit 5"
+        builder.limit(5).raw_sql.should match ignore_whitespace sql
+      end
+    end
   end
 {% end %}

spec/granite/query/builder_spec.cr

@@ -15,4 +15,14 @@ describe Granite::Query::Builder(Model) do
     ]
     query.order_fields.should eq expected
   end
+
+  it "stores limit" do
+    query = builder.limit(7)
+    query.limit.should eq 7
+  end
+
+  it "stores offset" do
+    query = builder.offset(17)
+    query.offset.should eq 17
+  end
 end

src/granite/query/assemblers/base.cr

@@ -26,6 +26,12 @@ module Granite::Query::Assembler
       [Model.fields].flatten.join ", "
     end
 
+    def build_sql
+      clauses = [] of String?
+      yield clauses
+      clauses.compact!.join " "
+    end
+
     abstract def count : Int64
     abstract def first(n : Int32 = 1) : Array(Model)
     abstract def delete

src/granite/query/assemblers/postgresql.cr

@@ -2,7 +2,15 @@
 # This will likely require adapter specific subclassing :[.
 module Granite::Query::Assembler
   class Postgresql(Model) < Base(Model)
-    def build_where
+    @where : String?
+    @order : String?
+    @limit : String?
+    @offset : String?
+    @group_by : String?
+
+    def where
+      return @where if @where
+
       clauses = @query.where_fields.map do |field, value|
         add_aggregate_field field
 
@@ -14,19 +22,21 @@ module Granite::Query::Assembler
         end
       end
 
-      return "" if clauses.none?
+      return nil if clauses.none?
 
-      "WHERE #{clauses.join " AND "}"
+      @where = "WHERE #{clauses.join " AND "}"
     end
 
-    def build_order(use_default_order = true)
+    def order(use_default_order = true)
+      return @order if @order
+
       order_fields = @query.order_fields
 
       if order_fields.none?
         if use_default_order
           order_fields = default_order
         else
-          return ""
+          return nil
         end
       end
 
@@ -40,7 +50,19 @@ module Granite::Query::Assembler
         end
       end
 
-      "ORDER BY #{order_clauses.join ", "}"
+      @order = "ORDER BY #{order_clauses.join ", "}"
+    end
+
+    def limit
+      @limit ||= if limit = @query.limit
+                   "LIMIT #{limit}"
+                 end
+    end
+
+    def offset
+      @offset ||= if offset = @query.offset
+                    "OFFSET #{offset}"
+                  end
     end
 
     def log(*stuff)
@@ -50,48 +72,42 @@ module Granite::Query::Assembler
       [{field: Model.primary_name, direction: "ASC"}]
     end
 
-    def build_group_by
-      if @aggregate_fields.any?
-        "GROUP BY #{@aggregate_fields.join ", "}"
-      else
-        ""
-      end
+    def group_by
+      @group_by ||= if @aggregate_fields.any?
+                      "GROUP BY #{@aggregate_fields.join ", "}"
+                    end
     end
 
     def count : Executor::Value(Model, Int64)
-      where = build_where
-      order = build_order(false)
-      group = build_group_by
-
-      sql = <<-SQL
-        SELECT COUNT(*)
-          FROM #{table_name}
-         #{where}
-         #{group}
-         #{order}
-      SQL
+      sql = build_sql do |s|
+        s << "SELECT COUNT(*)"
+        s << "FROM #{table_name}"
+        s << where
+        s << group_by
+        s << order
+      end
 
       Executor::Value(Model, Int64).new sql, numbered_parameters, default: 0_i64
     end
 
     def first(n : Int32 = 1) : Executor::List(Model)
-      sql = <<-SQL
-          SELECT #{field_list}
-            FROM #{table_name}
-           #{build_where}
-           #{build_order}
-           LIMIT #{n}
-      SQL
+      sql = build_sql do |s|
+        s << "SELECT #{field_list}"
+        s << "FROM #{table_name}"
+        s << where
+        s << order
+        s << "LIMIT #{n}"
+        s << offset
+      end
 
       Executor::List(Model).new sql, numbered_parameters
     end
 
     def delete
-      sql = <<-SQL
-         DELETE
-           FROM #{table_name}
-          #{build_where}
-      SQL
+      sql = build_sql do |s|
+        s << "DELETE FROM #{table_name}"
+        s << where
+      end
 
       log sql, numbered_parameters
       Model.adapter.open do |db|
@@ -100,12 +116,14 @@ module Granite::Query::Assembler
     end
 
     def select
-      sql = <<-SQL
-        SELECT #{field_list}
-          FROM #{table_name}
-          #{build_where}
-          #{build_order}
-      SQL
+      sql = build_sql do |s|
+        s << "SELECT #{field_list}"
+        s << "FROM #{table_name}"
+        s << where
+        s << order
+        s << limit
+        s << offset
+      end
 
       Executor::List(Model).new sql, numbered_parameters
     end

src/granite/query/builder.cr

@@ -24,12 +24,12 @@ class Granite::Query::Builder(Model)
     Descending
   end
 
-  getter where_fields
-  getter order_fields
+  getter where_fields = {} of FieldName => FieldData
+  getter order_fields = [] of NamedTuple(field: String, direction: Sort)
+  getter offset : Int64?
+  getter limit : Int64?
 
   def initialize(@boolean_operator = :and)
-    @where_fields = {} of FieldName => FieldData
-    @order_fields = [] of NamedTuple(field: String, direction: Sort)
   end
 
   def assembler
@@ -40,6 +40,10 @@ class Granite::Query::Builder(Model)
   end
 
   def where(**matches)
+    where(matches)
+  end
+
+  def where(matches)
     matches.each do |field, data|
       @where_fields[field.to_s] = data
     end
@@ -62,6 +66,10 @@ class Granite::Query::Builder(Model)
   end
 
   def order(**dsl)
+    order(dsl)
+  end
+
+  def order(dsl)
     dsl.each do |field, dsl_direction|
       direction = Sort::Ascending
 
@@ -75,6 +83,18 @@ class Granite::Query::Builder(Model)
     self
   end
 
+  def offset(num)
+    @offset = num.to_i64
+
+    self
+  end
+
+  def limit(num)
+    @limit = num.to_i64
+
+    self
+  end
+
   def raw_sql
     assembler.select.raw_sql
   end

src/granite/query/builder_methods.cr

@@ -1,27 +1,13 @@
-# DSL to be included into a model
+# DSL to be extended into a model
 # To activate, simply
 #
 # class Model < Granite::Base
-#   include Query::BuilderMethods
+#   extend Query::BuilderMethods
 # end
 module Granite::Query::BuilderMethods
   def __builder
     Builder(self).new
   end
 
-  def count : Executor::Value(self, Int64)
-    __builder.count
-  end
-
-  def where(**match_data) : Builder
-    __builder.where **match_data
-  end
-
-  def first : self?
-    __builder.first
-  end
-
-  def first(n : Int32) : Executor::List(self)
-    __builder.first n
-  end
+  delegate where, count, order, offset, limit, first, to: __builder
 end