From 0f5ab577bcc106aa487dd5b05ca0b991c9a96a04 Mon Sep 17 00:00:00 2001
From: Prajakta Bhosale <prajakta_b143@yahoo.co.in>
Date: Wed, 4 Feb 2015 11:23:41 -0600
Subject: [PATCH] Add support for UPDATE ... IF EXISTS

Patch by Prajakta Bhosale; reviewed by Tyler Hobbs for CASSANDRA-8610
---
 CHANGES.txt                                               | 1 +
 pylib/cqlshlib/cql3handling.py                            | 2 +-
 pylib/cqlshlib/helptopics.py                              | 3 ++-
 src/java/org/apache/cassandra/cql3/Cql.g                  | 6 ++++--
 .../apache/cassandra/cql3/statements/UpdateStatement.java | 8 +++++---
 5 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index 375dcfebcf..f4c96dc7eb 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,5 @@
 2.0.13:
+ * Add support for UPDATE ... IF EXISTS (CASSANDRA-8610)
  * Fix reversal of list prepends (CASSANDRA-8733)
  * Prevent non-zero default_time_to_live on tables with counters
    (CASSANDRA-8678)
diff --git a/pylib/cqlshlib/cql3handling.py b/pylib/cqlshlib/cql3handling.py
index 0b7863cc65..9e9b6ad4b6 100644
--- a/pylib/cqlshlib/cql3handling.py
+++ b/pylib/cqlshlib/cql3handling.py
@@ -15,7 +15,6 @@
 # limitations under the License.
 
 import re
-from warnings import warn
 from .cqlhandling import CqlParsingRuleSet, Hint
 from cql.cqltypes import (cql_types, lookup_casstype, CompositeType, UTF8Type,
                           ColumnToCollectionType, CounterColumnType, DateType)
@@ -715,6 +714,7 @@ syntax_rules += r'''
                                   ( "AND" [updateopt]=<usingOption> )* )?
                         "SET" <assignment> ( "," <assignment> )*
                         "WHERE" <whereClause>
+                        ( "IF" "EXISTS" )?
                     ;
 <assignment> ::= updatecol=<cident>
                     ( "=" update_rhs=( <value> | <cident> )
diff --git a/pylib/cqlshlib/helptopics.py b/pylib/cqlshlib/helptopics.py
index 2af8db2b53..0b08726eea 100644
--- a/pylib/cqlshlib/helptopics.py
+++ b/pylib/cqlshlib/helptopics.py
@@ -563,7 +563,8 @@ class CQL3HelpTopics(CQLHelpTopics):
         UPDATE [<keyspace>.]<columnFamily>
                               [USING [TIMESTAMP <timestamp>]
                                 [AND TTL <timeToLive>]]
-               SET name1 = value1, name2 = value2 WHERE <keycol> = keyval;
+               SET name1 = value1, name2 = value2 WHERE <keycol> = keyval
+               [IF EXISTS];
 
         An UPDATE is used to write one or more columns to a record in a table.
         No results are returned. The record's primary key must be completely
diff --git a/src/java/org/apache/cassandra/cql3/Cql.g b/src/java/org/apache/cassandra/cql3/Cql.g
index a80746c689..0595c251eb 100644
--- a/src/java/org/apache/cassandra/cql3/Cql.g
+++ b/src/java/org/apache/cassandra/cql3/Cql.g
@@ -360,18 +360,20 @@ updateStatement returns [UpdateStatement.ParsedUpdate expr]
     @init {
         Attributes.Raw attrs = new Attributes.Raw();
         List<Pair<ColumnIdentifier.Raw, Operation.RawUpdate>> operations = new ArrayList<Pair<ColumnIdentifier.Raw, Operation.RawUpdate>>();
+        boolean ifExists = false;
     }
     : K_UPDATE cf=columnFamilyName
       ( usingClause[attrs] )?
       K_SET columnOperation[operations] (',' columnOperation[operations])*
       K_WHERE wclause=whereClause
-      ( K_IF conditions=updateConditions )?
+      ( K_IF ( K_EXISTS { ifExists = true; } | conditions=updateConditions ))?
       {
           return new UpdateStatement.ParsedUpdate(cf,
                                                   attrs,
                                                   operations,
                                                   wclause,
-                                                  conditions == null ? Collections.<Pair<ColumnIdentifier.Raw, ColumnCondition.Raw>>emptyList() : conditions);
+                                                  conditions == null ? Collections.<Pair<ColumnIdentifier.Raw, ColumnCondition.Raw>>emptyList() : conditions,
+                                                  ifExists);
      }
     ;
 
diff --git a/src/java/org/apache/cassandra/cql3/statements/UpdateStatement.java b/src/java/org/apache/cassandra/cql3/statements/UpdateStatement.java
index 9d98c840ca..594b5db47e 100644
--- a/src/java/org/apache/cassandra/cql3/statements/UpdateStatement.java
+++ b/src/java/org/apache/cassandra/cql3/statements/UpdateStatement.java
@@ -207,14 +207,16 @@ public class UpdateStatement extends ModificationStatement
          * @param attrs additional attributes for statement (timestamp, timeToLive)
          * @param updates a map of column operations to perform
          * @param whereClause the where clause
-         */
+         * @param ifExists flag to check if row exists
+         * */
         public ParsedUpdate(CFName name,
                             Attributes.Raw attrs,
                             List<Pair<ColumnIdentifier.Raw, Operation.RawUpdate>> updates,
                             List<Relation> whereClause,
-                            List<Pair<ColumnIdentifier.Raw, ColumnCondition.Raw>> conditions)
+                            List<Pair<ColumnIdentifier.Raw, ColumnCondition.Raw>> conditions,
+                            boolean ifExists)
         {
-            super(name, attrs, conditions, false, false);
+            super(name, attrs, conditions, false, ifExists);
             this.updates = updates;
             this.whereClause = whereClause;
         }