Introduce xid8-based functions to replace txid_XXX.

The txid_XXX family of fmgr functions exposes 64 bit transaction IDs to
users as int8.  Now that we have an SQL type xid8 for FullTransactionId,
define a new set of functions including pg_current_xact_id() and
pg_current_snapshot() based on that.  Keep the old functions around too,
for now.

It's a bit sneaky to use the same C functions for both, but since the
binary representation is identical except for the signedness of the
type, and since older functions are the ones using the wrong signedness,
and since we'll presumably drop the older ones after a reasonable period
of time, it seems reasonable to switch to FullTransactionId internally
and share the code for both.

Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-by: Takao Fujii <btfujiitkp@oss.nttdata.com>
Reviewed-by: Yoshikazu Imai <imai.yoshikazu@fujitsu.com>
Reviewed-by: Mark Dilger <mark.dilger@enterprisedb.com>
Discussion: https://postgr.es/m/20190725000636.666m5mad25wfbrri%40alap3.anarazel.de

3 files changed, 4 insertions, 4 deletions

diff --git a/contrib/test_decoding/specs/oldest_xmin.spec b/contrib/test_decoding/specs/oldest_xmin.spec
index 6cb13e85cec..da3a8cd512d 100644
--- a/contrib/test_decoding/specs/oldest_xmin.spec
+++ b/contrib/test_decoding/specs/oldest_xmin.spec
@@ -19,7 +19,7 @@ teardown
 session "s0"
 setup { SET synchronous_commit=on; }
 step "s0_begin" { BEGIN; }
-step "s0_getxid" { SELECT txid_current() IS NULL; }
+step "s0_getxid" { SELECT pg_current_xact_id() IS NULL; }
 step "s0_alter" { ALTER TYPE basket DROP ATTRIBUTE mangos; }
 step "s0_commit" { COMMIT; }
 step "s0_checkpoint" { CHECKPOINT; }
diff --git a/contrib/test_decoding/specs/ondisk_startup.spec b/contrib/test_decoding/specs/ondisk_startup.spec
index 12c57a813da..96ce87f1a45 100644
--- a/contrib/test_decoding/specs/ondisk_startup.spec
+++ b/contrib/test_decoding/specs/ondisk_startup.spec
@@ -25,7 +25,7 @@ session "s2"
 setup { SET synchronous_commit=on; }
 
 step "s2b" { BEGIN; }
-step "s2txid" { SELECT txid_current() IS NULL; }
+step "s2txid" { SELECT pg_current_xact_id() IS NULL; }
 step "s2alter" { ALTER TABLE do_write ADD COLUMN addedbys2 int; }
 step "s2c" { COMMIT; }
 
@@ -34,7 +34,7 @@ session "s3"
 setup { SET synchronous_commit=on; }
 
 step "s3b" { BEGIN; }
-step "s3txid" { SELECT txid_current() IS NULL; }
+step "s3txid" { SELECT pg_current_xact_id() IS NULL; }
 step "s3c" { COMMIT; }
 
 # Force usage of ondisk snapshot by starting and not finishing a
diff --git a/contrib/test_decoding/specs/snapshot_transfer.spec b/contrib/test_decoding/specs/snapshot_transfer.spec
index ae81e8f102d..152f2fd03d9 100644
--- a/contrib/test_decoding/specs/snapshot_transfer.spec
+++ b/contrib/test_decoding/specs/snapshot_transfer.spec
@@ -20,7 +20,7 @@ session "s0"
 setup { SET synchronous_commit=on; }
 step "s0_begin" { BEGIN; }
 step "s0_begin_sub0" { SAVEPOINT s0; }
-step "s0_log_assignment" { SELECT txid_current() IS NULL; }
+step "s0_log_assignment" { SELECT pg_current_xact_id() IS NULL; }
 step "s0_begin_sub1" { SAVEPOINT s1; }
 step "s0_sub_get_base_snap" { INSERT INTO dummy VALUES (0); }
 step "s0_insert" { INSERT INTO harvest VALUES (1, 2, 3); }