Support MERGE WHEN NOT MATCHED BY SOURCE on PostgreSQL 17+

This adds the following dataset methods on PostgreSQL:

* merge_delete_when_not_matched_by_source
* merge_update_when_not_matched_by_source
* merge_do_nothing_when_not_matched_by_source

These are similar to the existing merge_delete, merge_update,
and merge_do_nothing_when_matched, except they use
WHEN NOT MATCHED BY SOURCE instead of WHEN MATCHED.

This replaces the _merge_matched_sql and _merge_not_matched_sql
private dataset methods with _merge_do_nothing_sql.

CHANGELOG

@@ -1,5 +1,7 @@
 === master
 
+* Support MERGE WHEN NOT MATCHED BY SOURCE on PostgreSQL 17+ (jeremyevans)
+
 * Add stdio_logger extension for a minimal logger that Sequel::Database can use (jeremyevans)
 
 * Simplify Database#inspect output to database_type, host, database, and user (jeremyevans)

lib/sequel/adapters/shared/postgres.rb

@@ -2068,6 +2068,19 @@ def merge(&block)
  end
  end
 
+ # Return a dataset with a WHEN NOT MATCHED BY SOURCE THEN DELETE 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.
+ #
+ # merge_delete_not_matched_by_source
+ # # WHEN NOT MATCHED BY SOURCE THEN DELETE
+ #
+ # merge_delete_not_matched_by_source{a > 30}
+ # # WHEN NOT MATCHED BY SOURCE AND (a > 30) THEN DELETE
+ def merge_delete_when_not_matched_by_source(&block)
+ _merge_when(:type=>:delete_not_matched_by_source, &block)
+ 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.
@@ -2094,6 +2107,19 @@ def merge_do_nothing_when_not_matched(&block)
  _merge_when(:type=>:not_matched, &block)
  end
 
+ # Return a dataset with a WHEN NOT MATCHED BY SOURCE THEN DO NOTHING clause added to the
+ # MERGE BY SOURCE statement. If a block is passed, treat it as a virtual row and
+ # use it as additional conditions for the match.
+ #
+ # merge_do_nothing_when_not_matched_by_source
+ # # WHEN NOT MATCHED BY SOURCE THEN DO NOTHING
+ #
+ # merge_do_nothing_when_not_matched_by_source{a > 30}
+ # # WHEN NOT MATCHED BY SOURCE AND (a > 30) THEN DO NOTHING
+ def merge_do_nothing_when_not_matched_by_source(&block)
+ _merge_when(:type=>:not_matched_by_source, &block)
+ end
+
  # Support OVERRIDING USER|SYSTEM VALUE for MERGE INSERT.
  def merge_insert(*values, &block)
  h = {:type=>:insert, :values=>values}
@@ -2103,6 +2129,19 @@ def merge_insert(*values, &block)
  _merge_when(h, &block)
  end
 
+ # Return a dataset with a WHEN NOT MATCHED BY SOURCE THEN UPDATE 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.
+ #
+ # merge_update_not_matched_by_source(i1: Sequel[:i1]+:i2+10, a: Sequel[:a]+:b+20)
+ # # WHEN NOT MATCHED BY SOURCE THEN UPDATE SET i1 = (i1 + i2 + 10), a = (a + b + 20)
+ #
+ # merge_update_not_matched_by_source(i1: :i2){a > 30}
+ # # WHEN NOT MATCHED BY SOURCE AND (a > 30) THEN UPDATE SET i1 = i2
+ def merge_update_when_not_matched_by_source(values, &block)
+ _merge_when(:type=>:update_not_matched_by_source, :values=>values, &block)
+ end
+
  # Use OVERRIDING USER VALUE for INSERT statements, so that identity columns
  # always use the user supplied value, and an error is not raised for identity
  # columns that are GENERATED ALWAYS.
@@ -2305,10 +2344,9 @@ def _merge_insert_sql(sql, data)
  _insert_values_sql(sql, values)
  end
 
- def _merge_matched_sql(sql, data)
+ def _merge_do_nothing_sql(sql, data)
  sql << " THEN DO NOTHING"
  end
- alias _merge_not_matched_sql _merge_matched_sql
 
  # Support MERGE RETURNING on PostgreSQL 17+.
  def _merge_when_sql(sql)

lib/sequel/dataset/sql.rb

@@ -901,18 +901,31 @@ def _merge_delete_sql(sql, data)
  MERGE_TYPE_SQL = {
  :insert => ' WHEN NOT MATCHED',
  :delete => ' WHEN MATCHED',
+ :delete_not_matched_by_source => ' WHEN NOT MATCHED BY SOURCE',
  :update => ' WHEN MATCHED',
+ :update_not_matched_by_source => ' WHEN NOT MATCHED BY SOURCE',
  :matched => ' WHEN MATCHED',
  :not_matched => ' WHEN NOT MATCHED',
+ :not_matched_by_source => ' WHEN NOT MATCHED BY SOURCE',
  }.freeze
  private_constant :MERGE_TYPE_SQL
 
+ MERGE_NORMALIZE_TYPE_MAP = {
+ :delete_not_matched_by_source => :delete,
+ :update_not_matched_by_source => :update,
+ :matched => :do_nothing,
+ :not_matched => :do_nothing,
+ :not_matched_by_source => :do_nothing,
+ }.freeze
+ private_constant :MERGE_NORMALIZE_TYPE_MAP
+
  # Add the WHEN clauses to the MERGE SQL
  def _merge_when_sql(sql)
  raise Error, "no WHEN [NOT] MATCHED clauses provided for MERGE" unless merge_when = @opts[:merge_when]
  merge_when.each do |data|
  type = data[:type]
  sql << MERGE_TYPE_SQL[type]
+ type = MERGE_NORMALIZE_TYPE_MAP[type] || type
  _merge_when_conditions_sql(sql, data)
  send(:"_merge_#{type}_sql", sql, data)
  end

spec/adapters/postgres_spec.rb

@@ -6030,3 +6030,48 @@ def check(ds)
  @m1.all.must_equal []
  end
 end if DB.server_version >= 170000
+
+describe "MERGE WHEN NOT MATCHED BY SOURCE" do
+ before(:all) do
+ @db = DB
+ @db.create_table!(:m1){Integer :i1; Integer :a}
+ @db.create_table!(:m2){Integer :i2}
+ @m1 = @db[:m1]
+ end
+ after do
+ @m1.delete
+ end
+ after(:all) do
+ @db.drop_table?(:m1, :m2)
+ end
+
+ it "should allow inserts, updates, do nothings, and deletes based on conditions in a single MERGE statement" do
+ ds = @m1.merge_using(:m2, :i1=>:i2)
+
+ @m1.insert(1, 2)
+ @m1.all.must_equal [{:i1=>1, :a=>2}]
+
+ ds.merge_do_nothing_when_not_matched_by_source.merge
+ @m1.all.must_equal [{:i1=>1, :a=>2}]
+
+ ds.merge_update_when_not_matched_by_source(:i1=>Sequel[:i1]+10, :a=>Sequel[:a]+20).merge
+ @m1.all.must_equal [{:i1=>11, :a=>22}]
+
+ ds.merge_delete_when_not_matched_by_source.merge
+ @m1.all.must_equal []
+
+ @m1.insert(1, 100)
+ @m1.insert(2, 40)
+ @m1.insert(3, 20)
+ @m1.insert(4, 5)
+
+ # conditions
+ ds.
+ merge_do_nothing_when_not_matched_by_source{a > 50}.
+ merge_delete_when_not_matched_by_source{a > 30}.
+ merge_update_when_not_matched_by_source(:a=>Sequel[:a]+20){a > 10}.
+ merge_update_when_not_matched_by_source(:a=>Sequel[:a]-20).
+ merge
+ @m1.order(:i1).all.must_equal [{:i1=>1, :a=>100}, {:i1=>3, :a=>40}, {:i1=>4, :a=>-15}]
+ end
+end if DB.server_version >= 170000