Avoid incrementing the CommandCounter when CommandCounterIncrement is called

but no database changes have been made since the last CommandCounterIncrement.
This should result in a significant improvement in the number of "commands"
that can typically be performed within a transaction before hitting the 2^32
CommandId size limit.  In particular this buys back (and more) the possible
adverse consequences of my previous patch to fix plan caching behavior.

The implementation requires tracking whether the current CommandCounter
value has been "used" to mark any tuples.  CommandCounter values stored into
snapshots are presumed not to be used for this purpose.  This requires some
small executor changes, since the executor used to conflate the curcid of
the snapshot it was using with the command ID to mark output tuples with.
Separating these concepts allows some small simplifications in executor APIs.

Something for the TODO list: look into having CommandCounterIncrement not do
AcceptInvalidationMessages.  It seems fairly bogus to be doing it there,
but exactly where to do it instead isn't clear, and I'm disinclined to mess
with asynchronous behavior during late beta.

2 files changed, 59 insertions, 159 deletions

diff --git a/src/test/regress/expected/combocid.out b/src/test/regress/expected/combocid.out
index 14e45fe489..b63894c283 100644
--- a/src/test/regress/expected/combocid.out
+++ b/src/test/regress/expected/combocid.out
@@ -4,66 +4,16 @@
 CREATE TEMP TABLE combocidtest (foobar int);
 BEGIN;
 -- a few dummy ops to push up the CommandId counter
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
 INSERT INTO combocidtest VALUES (1);
 INSERT INTO combocidtest VALUES (2);
 SELECT ctid,cmin,* FROM combocidtest;
@@ -79,8 +29,8 @@ UPDATE combocidtest SET foobar = foobar + 10;
 SELECT ctid,cmin,* FROM combocidtest;
  ctid  | cmin | foobar 
 -------+------+--------
- (0,3) |   13 |     11
- (0,4) |   13 |     12
+ (0,3) |   12 |     11
+ (0,4) |   12 |     12
 (2 rows)
 
 ROLLBACK TO s1;
@@ -109,8 +59,8 @@ DELETE FROM combocidtest;
 FETCH ALL FROM c;
  ctid  | cmin | foobar 
 -------+------+--------
- (0,1) |    2 |      1
- (0,2) |    2 |      2
+ (0,1) |    1 |      1
+ (0,2) |    1 |      2
  (0,5) |    0 |    333
 (3 rows)
 
@@ -118,79 +68,29 @@ ROLLBACK;
 SELECT ctid,cmin,* FROM combocidtest;
  ctid  | cmin | foobar 
 -------+------+--------
- (0,1) |    2 |      1
- (0,2) |    2 |      2
+ (0,1) |    1 |      1
+ (0,2) |    1 |      2
 (2 rows)
 
 -- check behavior with locked tuples
 BEGIN;
 -- a few dummy ops to push up the CommandId counter
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
-SELECT 1;
- ?column? 
-----------
-        1
-(1 row)
-
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
 INSERT INTO combocidtest VALUES (444);
 SELECT ctid,cmin,* FROM combocidtest;
  ctid  | cmin | foobar 
 -------+------+--------
- (0,1) |    2 |      1
- (0,2) |    2 |      2
+ (0,1) |    1 |      1
+ (0,2) |    1 |      2
  (0,6) |   10 |    444
 (3 rows)
 
@@ -199,16 +99,16 @@ SAVEPOINT s1;
 SELECT ctid,cmin,* FROM combocidtest FOR UPDATE;
  ctid  | cmin | foobar 
 -------+------+--------
- (0,1) |    2 |      1
- (0,2) |    2 |      2
+ (0,1) |    1 |      1
+ (0,2) |    1 |      2
  (0,6) |   10 |    444
 (3 rows)
 
 SELECT ctid,cmin,* FROM combocidtest;
  ctid  | cmin | foobar 
 -------+------+--------
- (0,1) |    2 |      1
- (0,2) |    2 |      2
+ (0,1) |    1 |      1
+ (0,2) |    1 |      2
  (0,6) |   10 |    444
 (3 rows)
 
@@ -217,17 +117,17 @@ UPDATE combocidtest SET foobar = foobar + 10;
 SELECT ctid,cmin,* FROM combocidtest;
  ctid  | cmin | foobar 
 -------+------+--------
- (0,7) |   14 |     11
- (0,8) |   14 |     12
- (0,9) |   14 |    454
+ (0,7) |   12 |     11
+ (0,8) |   12 |     12
+ (0,9) |   12 |    454
 (3 rows)
 
 ROLLBACK TO s1;
 SELECT ctid,cmin,* FROM combocidtest;
  ctid  | cmin | foobar 
 -------+------+--------
- (0,1) |   14 |      1
- (0,2) |   14 |      2
+ (0,1) |   12 |      1
+ (0,2) |   12 |      2
  (0,6) |    0 |    444
 (3 rows)
 
@@ -235,8 +135,8 @@ COMMIT;
 SELECT ctid,cmin,* FROM combocidtest;
  ctid  | cmin | foobar 
 -------+------+--------
- (0,1) |   14 |      1
- (0,2) |   14 |      2
+ (0,1) |   12 |      1
+ (0,2) |   12 |      2
  (0,6) |    0 |    444
 (3 rows)
 
diff --git a/src/test/regress/sql/combocid.sql b/src/test/regress/sql/combocid.sql
index 3f30839b1f..f24ac6b01a 100644
--- a/src/test/regress/sql/combocid.sql
+++ b/src/test/regress/sql/combocid.sql
@@ -6,16 +6,16 @@ CREATE TEMP TABLE combocidtest (foobar int);
 BEGIN;
 
 -- a few dummy ops to push up the CommandId counter
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
 
 INSERT INTO combocidtest VALUES (1);
 INSERT INTO combocidtest VALUES (2);
@@ -58,16 +58,16 @@ SELECT ctid,cmin,* FROM combocidtest;
 BEGIN;
 
 -- a few dummy ops to push up the CommandId counter
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
-SELECT 1;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
+INSERT INTO combocidtest SELECT 1 LIMIT 0;
 
 INSERT INTO combocidtest VALUES (444);