Support MERGE RETURNING on PostgreSQL 17+

CHANGELOG

@@ -1,5 +1,7 @@
 === master
 
+* Support MERGE RETURNING on PostgreSQL 17+ (jeremyevans)
+
 * Remove use of logger library in bin/sequel (jeremyevans)
 
 * Support :connect_opts_proc Database option for late binding options (jeremyevans) (#2164)

lib/sequel/adapters/shared/postgres.rb

@@ -2058,6 +2058,16 @@ def lock(mode, opts=OPTS)
  nil
  end
 
+ # Support MERGE RETURNING on PostgreSQL 17+.
+ def merge(&block)
+ sql = merge_sql
+ if uses_returning?(:merge)
+ returning_fetch_rows(sql, &block)
+ else
+ execute_ddl(sql)
+ end
+ end
+
  # Return a dataset with a WHEN MATCHED THEN DO NOTHING clause added to the
  # MERGE statement. If a block is passed, treat it as a virtual row and
  # use it as additional conditions for the match.
@@ -2170,9 +2180,14 @@ def supports_nowait?
  true
  end
 
- # Returning is always supported.
+ # MERGE RETURNING is supported on PostgreSQL 17+. Other RETURNING is supported
+ # on all supported PostgreSQL versions.
  def supports_returning?(type)
- true
+ if type == :merge
+ server_version >= 170000
+ else
+ true
+ end
  end
 
  # PostgreSQL supports pattern matching via regular expressions
@@ -2295,6 +2310,12 @@ def _merge_matched_sql(sql, data)
  end
  alias _merge_not_matched_sql _merge_matched_sql
 
+ # Support MERGE RETURNING on PostgreSQL 17+.
+ def _merge_when_sql(sql)
+ super
+ insert_returning_sql(sql) if uses_returning?(:merge)
+ end
+
  # Format TRUNCATE statement with PostgreSQL specific options.
  def _truncate_sql(table)
  to = @opts[:truncate_opts] || OPTS

spec/adapters/postgres_spec.rb

@@ -5928,3 +5928,105 @@ def c2.name; 'Bar' end
  end
  end
 end
+
+
+describe "MERGE RETURNING" do
+ before(:all) do
+ @db = DB
+ @db.create_table!(:m1){Integer :i1; Integer :a}
+ @db.create_table!(:m2){Integer :i2; Integer :b}
+ @m1 = @db[:m1].returning
+ @m2 = @db[:m2]
+ end
+ after do
+ @m1.delete
+ @m2.delete
+ end
+ after(:all) do
+ @db.drop_table?(:m1, :m2)
+ end
+
+ def merge(ds)
+ a = []
+ ds.merge{|h| a << h}
+ a
+ end
+
+ def check(ds)
+ @m2.insert(1, 2)
+
+ @m1.all.must_equal []
+
+ # INSERT
+ merge(ds).must_equal [{:i2=>1, :b=>2, :i1=>1, :a=>13}]
+ @m1.all.must_equal [{:i1=>1, :a=>13}]
+
+ # UPDATE
+ merge(ds).must_equal [{:i2=>1, :b=>2, :i1=>12, :a=>35}]
+ @m1.all.must_equal [{:i1=>12, :a=>35}]
+
+ # UPDATE with specific RETURNING columns
+ @m1.update(:i1=>1, :a=>13)
+ merge(ds.returning(:b)).must_equal [{:b=>2}]
+ @m1.all.must_equal [{:i1=>12, :a=>35}]
+
+ # DELETE MATCHING current row, INSERT NOT MATCHED new row
+ @m2.insert(12, 3)
+ merge(ds).must_equal [{:i2=>1, :b=>2, :i1=>1, :a=>13}, {:i2=>12, :b=>3, :i1=>12, :a=>35}]
+ @m1.all.must_equal [{:i1=>1, :a=>13}]
+
+ # MATCHED DO NOTHING
+ @m2.where(:i2=>12).delete
+ @m1.update(:a=>51)
+ merge(ds).must_equal []
+ @m1.all.must_equal [{:i1=>1, :a=>51}]
+
+ # NOT MATCHED DO NOTHING
+ @m1.delete
+ @m2.update(:b=>51)
+ merge(ds).must_equal []
+ @m1.all.must_equal []
+ end
+
+ it "should allow inserts, updates, and deletes based on conditions in a single MERGE statement" do
+ ds = @m1.
+ merge_using(:m2, :i1=>:i2).
+ merge_insert(:i1=>Sequel[:i2], :a=>Sequel[:b]+11){b <= 50}.
+ merge_delete{{:a => 30..50}}.
+ merge_update(:i1=>Sequel[:i1]+:i2+10, :a=>Sequel[:a]+:b+20){a <= 50}
+ check(ds)
+ end
+
+ it "should support WITH clauses" do
+ ds = @m1.
+ with(:m3, @db[:m2]).
+ merge_using(:m3, :i1=>:i2).
+ merge_insert(:i1=>Sequel[:i2], :a=>Sequel[:b]+11){b <= 50}.
+ merge_delete{{:a => 30..50}}.
+ merge_update(:i1=>Sequel[:i1]+:i2+10, :a=>Sequel[:a]+:b+20){a <= 50}
+ check(ds)
+ end if DB.dataset.supports_cte?
+
+ it "should support inserts with just columns" do
+ ds = @m1.
+ merge_using(:m2, :i1=>:i2).
+ merge_insert(Sequel[:i2], Sequel[:b]+11){b <= 50}.
+ merge_delete{{:a => 30..50}}.
+ merge_update(:i1=>Sequel[:i1]+:i2+10, :a=>Sequel[:a]+:b+20){a <= 50}
+ check(ds)
+ end
+
+ it "should calls inserts, updates, and deletes without conditions" do
+ @m2.insert(1, 2)
+ ds = @m1.merge_using(:m2, :i1=>:i2)
+
+ merge(ds.merge_insert(:i2, :b)).must_equal [{:i2=>1, :b=>2, :i1=>1, :a=>2}]
+ @m1.all.must_equal [{:i1=>1, :a=>2}]
+
+ merge(ds.merge_update(:a=>Sequel[:a]+1)).must_equal [{:i2=>1, :b=>2, :i1=>1, :a=>3}]
+ @m1.all.must_equal [{:i1=>1, :a=>3}]
+
+ merge(ds.merge_delete).must_equal [{:i2=>1, :b=>2, :i1=>1, :a=>3}]
+ @m1.all.must_equal []
+ end
+end if DB.server_version >= 170000