tableam: Add tuple_{insert, delete, update, lock} and use.

This adds new, required, table AM callbacks for insert/delete/update
and lock_tuple. To be able to reasonably use those, the EvalPlanQual
mechanism had to be adapted, moving more logic into the AM.

Previously both delete/update/lock call-sites and the EPQ mechanism had
to have awareness of the specific tuple format to be able to fetch the
latest version of a tuple. Obviously that needs to be abstracted
away. To do so, move the logic that find the latest row version into
the AM. lock_tuple has a new flag argument,
TUPLE_LOCK_FLAG_FIND_LAST_VERSION, that forces it to lock the last
version, rather than the current one.  It'd have been possible to do
so via a separate callback as well, but finding the last version
usually also necessitates locking the newest version, making it
sensible to combine the two. This replaces the previous use of
EvalPlanQualFetch().  Additionally HeapTupleUpdated, which previously
signaled either a concurrent update or delete, is now split into two,
to avoid callers needing AM specific knowledge to differentiate.

The move of finding the latest row version into tuple_lock means that
encountering a row concurrently moved into another partition will now
raise an error about "tuple to be locked" rather than "tuple to be
updated/deleted" - which is accurate, as that always happens when
locking rows. While possible slightly less helpful for users, it seems
like an acceptable trade-off.

As part of this commit HTSU_Result has been renamed to TM_Result, and
its members been expanded to differentiated between updating and
deleting. HeapUpdateFailureData has been renamed to TM_FailureData.

The interface to speculative insertion is changed so nodeModifyTable.c
does not have to set the speculative token itself anymore. Instead
there's a version of tuple_insert, tuple_insert_speculative, that
performs the speculative insertion (without requiring a flag to signal
that fact), and the speculative insertion is either made permanent
with table_complete_speculative(succeeded = true) or aborted with
succeeded = false).

Note that multi_insert is not yet routed through tableam, nor is
COPY. Changing multi_insert requires changes to copy.c that are large
enough to better be done separately.

Similarly, although simpler, CREATE TABLE AS and CREATE MATERIALIZED
VIEW are also only going to be adjusted in a later commit.

Author: Andres Freund and Haribabu Kommi
Discussion:
    https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de
    https://postgr.es/m/20190313003903.nwvrxi7rw3ywhdel@alap3.anarazel.de
    https://postgr.es/m/20160812231527.GA690404@alvherre.pgsql

src/backend/access/table/tableam.c

@@ -176,6 +176,119 @@ table_beginscan_parallel(Relation relation, ParallelTableScanDesc parallel_scan)
 }
 
 
+/* ----------------------------------------------------------------------------
+ * Functions to make modifications a bit simpler.
+ * ----------------------------------------------------------------------------
+ */
+
+/*
+ * simple_table_insert - insert a tuple
+ *
+ * Currently, this routine differs from table_insert only in supplying a
+ * default command ID and not allowing access to the speedup options.
+ */
+void
+simple_table_insert(Relation rel, TupleTableSlot *slot)
+{
+	table_insert(rel, slot, GetCurrentCommandId(true), 0, NULL);
+}
+
+/*
+ * simple_table_delete - delete a tuple
+ *
+ * This routine may be used to delete a tuple when concurrent updates of
+ * the target tuple are not expected (for example, because we have a lock
+ * on the relation associated with the tuple).  Any failure is reported
+ * via ereport().
+ */
+void
+simple_table_delete(Relation rel, ItemPointer tid, Snapshot snapshot)
+{
+	TM_Result	result;
+	TM_FailureData tmfd;
+
+	result = table_delete(rel, tid,
+						  GetCurrentCommandId(true),
+						  snapshot, InvalidSnapshot,
+						  true /* wait for commit */ ,
+						  &tmfd, false /* changingPart */ );
+
+	switch (result)
+	{
+		case TM_SelfModified:
+			/* Tuple was already updated in current command? */
+			elog(ERROR, "tuple already updated by self");
+			break;
+
+		case TM_Ok:
+			/* done successfully */
+			break;
+
+		case TM_Updated:
+			elog(ERROR, "tuple concurrently updated");
+			break;
+
+		case TM_Deleted:
+			elog(ERROR, "tuple concurrently deleted");
+			break;
+
+		default:
+			elog(ERROR, "unrecognized table_delete status: %u", result);
+			break;
+	}
+}
+
+/*
+ * simple_table_update - replace a tuple
+ *
+ * This routine may be used to update a tuple when concurrent updates of
+ * the target tuple are not expected (for example, because we have a lock
+ * on the relation associated with the tuple).  Any failure is reported
+ * via ereport().
+ */
+void
+simple_table_update(Relation rel, ItemPointer otid,
+					TupleTableSlot *slot,
+					Snapshot snapshot,
+					bool *update_indexes)
+{
+	TM_Result	result;
+	TM_FailureData tmfd;
+	LockTupleMode lockmode;
+
+	result = table_update(rel, otid, slot,
+						  GetCurrentCommandId(true),
+						  snapshot, InvalidSnapshot,
+						  true /* wait for commit */ ,
+						  &tmfd, &lockmode, update_indexes);
+
+	switch (result)
+	{
+		case TM_SelfModified:
+			/* Tuple was already updated in current command? */
+			elog(ERROR, "tuple already updated by self");
+			break;
+
+		case TM_Ok:
+			/* done successfully */
+			break;
+
+		case TM_Updated:
+			elog(ERROR, "tuple concurrently updated");
+			break;
+
+		case TM_Deleted:
+			elog(ERROR, "tuple concurrently deleted");
+			break;
+
+		default:
+			elog(ERROR, "unrecognized table_update status: %u", result);
+			break;
+	}
+
+}
+
+
 /* ----------------------------------------------------------------------------
  * Helper functions to implement parallel scans for block oriented AMs.
  * ----------------------------------------------------------------------------