CASSANDRA-21484 - Support IF, ELSE IF, and ELSE for transaction statements

.gitmodules

@@ -1,4 +1,4 @@
 [submodule "modules/accord"]
 	path = modules/accord
-	url = https://github.com/apache/cassandra-accord.git
-	branch = trunk
+	url = https://github.com/alanwang67/cassandra-accord.git
+	branch = linearIntersectionBug

doc/modules/cassandra/pages/developing/cql/transactions.adoc

@@ -318,12 +318,26 @@ END IF
 IF account_info IS NOT NULL AND account_info.balance > 0 THEN
   -- statements
 END IF
+
+-- IF, ELSE IF, ELSE conditions
+IF account_info IS NOT NULL AND account_info.balance > 0 THEN
+  -- statements
+ELSE IF account_info.balance < 0 THEN
+  -- statements
+ELSE
+  -- statements
+END IF
+
+-- Trailing update after conditions
+IF account_info IS NOT NULL AND account_info.balance > 0 THEN
+  -- statements
+-- statements
+END IF
 ----
 
 **Important Notes:**
 
 * Null handling is strict (any null comparison returns false)
-* All modification statements must be inside the IF block when using conditions
 
 == Restrictions
 
@@ -354,6 +368,11 @@ BEGIN TRANSACTION
   [SELECT selectStatement | SELECT rowDataReferences]
   [IF conditionalExpression THEN]
     [modificationStatements]
+  [ELSE IF conditionalExpression THEN]
+    [modificationStatements]
+  [ELSE]
+    [modificationStatements]
+  [modificationStatements]
   [END IF]
 COMMIT TRANSACTION
 ----

src/antlr/Lexer.g

@@ -128,6 +128,7 @@ K_ALLOW:       A L L O W;
 K_FILTERING:   F I L T E R I N G;
 K_IF:          I F;
 K_THEN:        T H E N;
+K_ELSE:        E L S E;
 K_END:         E N D;
 K_IS:          I S;
 K_CONTAINS:    C O N T A I N S;

src/antlr/Parser.g

@@ -29,8 +29,6 @@ options {
 
     // enables parsing txn specific syntax when true
     protected boolean isParsingTxn = false;
-    // tracks whether a txn has conditional updates
-    protected boolean isTxnConditional = false;
 
     protected List<RowDataReference.Raw> references;
 
@@ -783,20 +781,33 @@ batchTxnStatement returns [TransactionStatement.Parsed expr]
         List<SelectStatement.RawStatement> assignments = new ArrayList<>();
         SelectStatement.RawStatement select = null;
         List<RowDataReference.Raw> returning = null;
-        List<ModificationStatement.Parsed> updates = new ArrayList<>();
+        List<List<ConditionStatement.Raw>> conditions = new ArrayList<>();
+        List<List<ModificationStatement.Parsed>> updates = new ArrayList<>();
     }
     : K_BEGIN K_TRANSACTION
       ( let=letStatement ';' { assignments.add(let); })*
       ( ( (selectStatement) => s=selectStatement ';' { select = s; }) | ( K_SELECT drs=rowDataReferences ';' { returning = drs; }) )?
-      ( K_IF conditions=txnConditions K_THEN { isTxnConditional = true; } )?
-      ( upd=batchStatementObjective ';' { updates.add(upd); } )*
-      ( {!isTxnConditional}? (K_COMMIT K_TRANSACTION) | {isTxnConditional}? (K_END K_IF K_COMMIT K_TRANSACTION))
+      (
+          K_IF c=txnConditions K_THEN u=updateStatements { conditions.add(c); updates.add(u); }
+          ( K_ELSE K_IF c=txnConditions K_THEN u=updateStatements { conditions.add(c); updates.add(u); } )*
+          ( K_ELSE u=updateStatements { conditions.add(Collections.singletonList(new ConditionStatement.Raw(null, ConditionStatement.Kind.ELSE, null))); updates.add(u); } )?
+          K_END K_IF
+      )?
+      ( (updateStatements) => u=updateStatements { if (!u.isEmpty()) updates.add(u); } )?
+      (K_COMMIT K_TRANSACTION)
     {
         $expr = new TransactionStatement.Parsed(assignments, select, returning, updates, conditions, references);
     }
     ;
     finally { isParsingTxn = false; }
 
+updateStatements returns [List<ModificationStatement.Parsed> updates]
+    @init {
+        updates = new ArrayList<ModificationStatement.Parsed>();
+    }
+    : (upd=batchStatementObjective ';' { updates.add(upd); })*
+    ;
+
 rowDataReferences returns [List<RowDataReference.Raw> refs]
     : r1=rowDataReference { refs = new ArrayList<RowDataReference.Raw>(); refs.add(r1); } (',' rN=rowDataReference { refs.add(rN); })*
     ;
@@ -2473,6 +2484,7 @@ basic_unreserved_keyword returns [String str]
         | K_END
         | K_LET
         | K_THEN
+        | K_ELSE
         | K_TRANSACTION
         | K_COMMENT
         | K_COMMENTS

src/java/org/apache/cassandra/cql3/transactions/ConditionStatement.java

@@ -40,13 +40,14 @@ public enum Kind
         GT(TxnCondition.Kind.GREATER_THAN, TxnCondition.Kind.LESS_THAN),
         GTE(TxnCondition.Kind.GREATER_THAN_OR_EQUAL, TxnCondition.Kind.LESS_THAN_OR_EQUAL),
         LT(TxnCondition.Kind.LESS_THAN, TxnCondition.Kind.GREATER_THAN),
-        LTE(TxnCondition.Kind.LESS_THAN_OR_EQUAL, TxnCondition.Kind.GREATER_THAN_OR_EQUAL);
-
+        LTE(TxnCondition.Kind.LESS_THAN_OR_EQUAL, TxnCondition.Kind.GREATER_THAN_OR_EQUAL),
+        ELSE(TxnCondition.Kind.ELSE, null);
+
         // TODO: Support for IN, CONTAINS, CONTAINS KEY
 
         private final TxnCondition.Kind kind;
         private final TxnCondition.Kind reversedKind;
-        
+
         Kind(TxnCondition.Kind kind, TxnCondition.Kind reversedKind)
         {
             this.kind = kind;
@@ -80,15 +81,18 @@ public static class Raw
 
         public Raw(Term.Raw lhs, Kind kind, Term.Raw rhs)
         {
-            Preconditions.checkArgument(lhs != null);
-            Preconditions.checkArgument((rhs == null) == (kind == Kind.IS_NOT_NULL || kind == Kind.IS_NULL));
+            Preconditions.checkArgument(lhs != null || kind == Kind.ELSE);
+            Preconditions.checkArgument((rhs == null) == (kind == Kind.IS_NOT_NULL || kind == Kind.IS_NULL || kind == Kind.ELSE));
             this.lhs = lhs;
             this.kind = kind;
             this.rhs = rhs;
         }
 
         public ConditionStatement prepare(String keyspace, VariableSpecifications bindVariables)
         {
+            if (kind == Kind.ELSE)
+                return new ConditionStatement(null, kind, null, false);
+
             if (rhs == null)
             {
                 // In the IS NULL/IS NOT NULL case, the reference will always be on the LHS
@@ -134,6 +138,8 @@ public TxnCondition createCondition(QueryOptions options)
     {
         switch (kind)
         {
+            case ELSE:
+                return TxnCondition.Else.instance;
             case IS_NOT_NULL:
             case IS_NULL:
                 return new TxnCondition.Exists(reference.toTxnReference(options), kind.toTxnKind(reversed));

src/java/org/apache/cassandra/service/accord/txn/TxnCondition.java

@@ -117,7 +117,8 @@ public enum Kind
         GREATER_THAN_OR_EQUAL(">=", Operator.GTE),
         LESS_THAN("<", Operator.LT),
         LESS_THAN_OR_EQUAL("<=", Operator.LTE),
-        COLUMN_CONDITIONS("COLUMN_CONDITIONS", null);
+        COLUMN_CONDITIONS("COLUMN_CONDITIONS", null),
+        ELSE("ELSE", null);
 
         @Nonnull
         private final String symbol;
@@ -152,6 +153,8 @@ private ConditionSerializer serializer()
                     return None.serializer;
                 case COLUMN_CONDITIONS:
                     return ColumnConditionsAdapter.serializer;
+                case ELSE:
+                    return Else.serializer;
                 default:
                     throw new IllegalArgumentException("No serializer exists for kind " + this);
             }
@@ -231,6 +234,43 @@ public static TxnCondition none()
         return None.instance;
     }
 
+    public static class Else extends TxnCondition
+    {
+        public static final Else instance = new Else();
+
+        private Else()
+        {
+            super(Kind.ELSE);
+        }
+
+        @Override
+        public String toString()
+        {
+            return kind.toString();
+        }
+
+        @Override
+        public void collect(TableMetadatas.Collector collector)
+        {
+        }
+
+        @Override
+        public boolean applies(TxnData data)
+        {
+            return true;
+        }
+
+        private static final ConditionSerializer<Else> serializer = new ConditionSerializer<>()
+        {
+            @Override
+            public void serialize(Else condition, TableMetadatas tables, DataOutputPlus out) {}
+            @Override
+            public Else deserialize(TableMetadatas tables, DataInputPlus in, Kind kind) { return instance; }
+            @Override
+            public long serializedSize(Else condition, TableMetadatas tables) { return 0; }
+        };
+    }
+
     public static class Exists extends TxnCondition
     {
         private static final Set<Kind> KINDS = ImmutableSet.of(Kind.IS_NOT_NULL, Kind.IS_NULL);