Don't create versions that would be identical to previous version (#35)

test/expected/unchanged_version_values.out

@@ -0,0 +1,58 @@
+CREATE TABLE versioning (a bigint, b bigint, sys_period tstzrange);
+-- Insert some data before versioning is enabled.
+INSERT INTO versioning (a, b, sys_period) VALUES (2, 2, tstzrange('2000-01-01', NULL));
+CREATE TABLE versioning_history (b bigint, sys_period tstzrange);
+CREATE TRIGGER versioning_trigger
+BEFORE INSERT OR UPDATE OR DELETE ON versioning
+FOR EACH ROW EXECUTE PROCEDURE versioning('sys_period', 'versioning_history', false, true);
+-- Update with no changes that would affect history
+BEGIN;
+UPDATE versioning SET a = 3;
+SELECT a, b FROM versioning ORDER BY a, sys_period;
+ a | b
+---+---
+ 3 | 2
+(1 row)
+
+SELECT b, upper(sys_period) = CURRENT_TIMESTAMP FROM versioning_history ORDER BY b, sys_period;
+ b | ?column? 
+---+----------
+(0 rows)
+
+SELECT a, b FROM versioning WHERE lower(sys_period) = CURRENT_TIMESTAMP ORDER BY a, sys_period;
+ a | b 
+---+---
+(0 rows)
+
+COMMIT;
+-- Make sure that the next transaction's CURRENT_TIMESTAMP is different.
+SELECT pg_sleep(0.1);
+ pg_sleep 
+----------
+
+(1 row)
+
+-- Update with changes that would affect history.
+BEGIN;
+UPDATE versioning SET b = 3;
+SELECT a, b, lower(sys_period) = CURRENT_TIMESTAMP FROM versioning ORDER BY a, sys_period;
+ a | b | ?column? 
+---+---+----------
+ 3 | 3 | t
+(1 row)
+
+SELECT b, upper(sys_period) = CURRENT_TIMESTAMP FROM versioning_history ORDER BY b, sys_period;
+ b | ?column? 
+---+----------
+ 2 | t
+(1 row)
+
+SELECT a, b FROM versioning WHERE lower(sys_period) = CURRENT_TIMESTAMP ORDER BY a, sys_period;
+ a | b 
+---+---
+ 3 | 3
+(1 row)
+
+COMMIT;
+DROP TABLE versioning;
+DROP TABLE versioning_history;

test/runTest.sh

@@ -9,7 +9,7 @@ TESTS="
  no_history_table no_history_system_period no_system_period
  invalid_system_period_values invalid_system_period invalid_types
  versioning upper_case structure combinations
- different_schema unchanged_values"
+ different_schema unchanged_values unchanged_version_values"
 
 for name in $TESTS; do
  echo ""

test/runTestNochecks.sh

@@ -5,7 +5,9 @@ psql temporal_tables_test -q -f versioning_function_nochecks.sql
 
 mkdir -p test/result
 
-TESTS="versioning upper_case structure combinations different_schema unchanged_values"
+TESTS="
+ versioning upper_case structure combinations different_schema unchanged_values
+ unchanged_version_values"
 
 for name in $TESTS; do
  echo ""

test/sql/unchanged_version_values.sql

@@ -0,0 +1,42 @@
+CREATE TABLE versioning (a bigint, b bigint, sys_period tstzrange);
+
+-- Insert some data before versioning is enabled.
+INSERT INTO versioning (a, b, sys_period) VALUES (2, 2, tstzrange('2000-01-01', NULL));
+
+CREATE TABLE versioning_history (b bigint, sys_period tstzrange);
+
+CREATE TRIGGER versioning_trigger
+BEFORE INSERT OR UPDATE OR DELETE ON versioning
+FOR EACH ROW EXECUTE PROCEDURE versioning('sys_period', 'versioning_history', false, true);
+
+-- Update with no changes that would affect history
+BEGIN;
+
+UPDATE versioning SET a = 3;
+
+SELECT a, b FROM versioning ORDER BY a, sys_period;
+
+SELECT b, upper(sys_period) = CURRENT_TIMESTAMP FROM versioning_history ORDER BY b, sys_period;
+
+SELECT a, b FROM versioning WHERE lower(sys_period) = CURRENT_TIMESTAMP ORDER BY a, sys_period;
+
+COMMIT;
+
+-- Make sure that the next transaction's CURRENT_TIMESTAMP is different.
+SELECT pg_sleep(0.1);
+
+-- Update with changes that would affect history.
+BEGIN;
+
+UPDATE versioning SET b = 3;
+
+SELECT a, b, lower(sys_period) = CURRENT_TIMESTAMP FROM versioning ORDER BY a, sys_period;
+
+SELECT b, upper(sys_period) = CURRENT_TIMESTAMP FROM versioning_history ORDER BY b, sys_period;
+
+SELECT a, b FROM versioning WHERE lower(sys_period) = CURRENT_TIMESTAMP ORDER BY a, sys_period;
+
+COMMIT;
+
+DROP TABLE versioning;
+DROP TABLE versioning_history;

versioning_function.sql

@@ -15,6 +15,8 @@ DECLARE
  holder record;
  holder2 record;
  pg_version integer;
+ newVersion record;
+ oldVersion record;
 BEGIN
 
  IF TG_WHEN != 'BEFORE' OR TG_LEVEL != 'ROW' THEN
@@ -37,10 +39,6 @@ BEGIN
  history_table := TG_ARGV[1];
  ignore_unchanged_values := TG_ARGV[3];
 
- IF ignore_unchanged_values AND TG_OP = 'UPDATE' AND NEW IS NOT DISTINCT FROM OLD THEN
- RETURN OLD;
- END IF;
-
  -- check if sys_period exists on original table
  SELECT atttypid, attndims INTO holder FROM pg_attribute WHERE attrelid = TG_RELID AND attname = sys_period AND NOT attisdropped;
  IF NOT FOUND THEN
@@ -164,7 +162,18 @@ BEGIN
  INNER JOIN main
  ON history.attname = main.attname
  AND history.attname != sys_period;
-
+ -- skip version if it would be identical to the previous version
+ IF ignore_unchanged_values AND TG_OP = 'UPDATE' AND array_length(commonColumns, 1) > 0 THEN
+ EXECUTE 'SELECT ROW($1.' || array_to_string(commonColumns , ', $1.') || ')'
+ USING NEW
+ INTO newVersion;
+ EXECUTE 'SELECT ROW($1.' || array_to_string(commonColumns , ', $1.') || ')'
+ USING OLD
+ INTO oldVersion;
+ IF newVersion IS NOT DISTINCT FROM oldVersion THEN
+ RETURN NEW;
+ END IF;
+ END IF;
  EXECUTE ('INSERT INTO ' ||
  history_table ||
  '(' ||

versioning_function_nochecks.sql

@@ -12,15 +12,14 @@ DECLARE
  range_lower timestamptz;
  transaction_info txid_snapshot;
  existing_range tstzrange;
+ newVersion record;
+ oldVersion record;
 BEGIN
 
  sys_period := TG_ARGV[0];
  history_table := TG_ARGV[1];
  ignore_unchanged_values := TG_ARGV[3];
 
- IF ignore_unchanged_values AND TG_OP = 'UPDATE' AND NEW IS NOT DISTINCT FROM OLD THEN
- RETURN OLD;
- END IF;
 
  IF TG_OP = 'UPDATE' OR TG_OP = 'DELETE' THEN
  -- Ignore rows already modified in this transaction
@@ -61,7 +60,17 @@ BEGIN
  INNER JOIN main
  ON history.attname = main.attname
  AND history.attname != sys_period;
-
+ -- skip version if it would be identical to the previous version
+ IF ignore_unchanged_values AND TG_OP = 'UPDATE' AND array_length(commonColumns, 1) > 0 THEN EXECUTE 'SELECT ROW($1.' || array_to_string(commonColumns , ', $1.') || ')'
+ USING NEW
+ INTO newVersion;
+ EXECUTE 'SELECT ROW($1.' || array_to_string(commonColumns , ', $1.') || ')'
+ USING OLD
+ INTO oldVersion;
+ IF newVersion IS NOT DISTINCT FROM oldVersion THEN
+ RETURN NEW;
+ END IF;
+ END IF;
  EXECUTE ('INSERT INTO ' ||
  history_table ||
  '(' ||