support clickhouse asof join

src/main/java/com/alibaba/druid/sql/ast/statement/SQLJoinTableSource.java

@@ -37,6 +37,7 @@ public class SQLJoinTableSource extends SQLTableSourceImpl implements SQLReplace
     protected final List<SQLExpr> using = new ArrayList<SQLExpr>();
     protected boolean             natural = false;
     protected UDJ                 udj; // for maxcompute
+    protected boolean             asof; // for clickhouse
 
     public SQLJoinTableSource(String alias){
         super(alias);
@@ -93,6 +94,14 @@ public class SQLJoinTableSource extends SQLTableSourceImpl implements SQLReplace
         this.udj = x;
     }
 
+    public boolean isAsof() {
+        return asof;
+    }
+
+    public void setAsof(boolean asof) {
+        this.asof = asof;
+    }
+
     public JoinType getJoinType() {
         return this.joinType;
     }
@@ -324,6 +333,7 @@ public class SQLJoinTableSource extends SQLTableSourceImpl implements SQLReplace
         }
 
         x.natural = natural;
+        x.asof = asof;
 
         if (udj != null) {
             x.udj = udj.clone();
@@ -348,6 +358,7 @@ public class SQLJoinTableSource extends SQLTableSourceImpl implements SQLReplace
         if (right instanceof SQLJoinTableSource) {
             ((SQLJoinTableSource) right).reverse();
         }
+
     }
 
     /**

src/main/java/com/alibaba/druid/sql/parser/SQLParser.java

@@ -154,6 +154,14 @@ public class SQLParser {
                         return null;
                     }
                     return ident;
+                } else if (hash == FnvHash.Constants.ASOF && dbType == DbType.clickhouse) {
+                    Lexer.SavePoint mark = lexer.mark();
+                    lexer.nextToken();
+                    if (lexer.token == Token.LEFT || lexer.token == Token.JOIN) {
+                        lexer.reset(mark);
+                        return null;
+                    }
+                    return ident;
                 }
             }
         }

src/main/java/com/alibaba/druid/sql/parser/SQLSelectParser.java

@@ -1151,7 +1151,7 @@ public class SQLSelectParser extends SQLParser {
                             && ((hash = lexer.hash_lower()) == FnvHash.Constants.STRAIGHT_JOIN
                             || hash == FnvHash.Constants.CROSS)))
                     {
-                        String alias = tableAlias();
+                        String alias = tableAlias(false);
                         if (alias != null) {
                             if (isEnabled(SQLParserFeature.IgnoreNameQuotes) && alias.length() > 1) {
                                 alias = StringUtils.removeNameQuotes(alias);
@@ -1192,6 +1192,12 @@ public class SQLSelectParser extends SQLParser {
             lexer.nextToken();
         }
 
+        boolean asof = false;
+        if (lexer.identifierEquals(FnvHash.Constants.ASOF) && dbType == DbType.clickhouse) {
+            lexer.nextToken();
+            asof = true;
+        }
+
         switch (lexer.token) {
             case LEFT:
                 lexer.nextToken();
@@ -1276,6 +1282,9 @@ public class SQLSelectParser extends SQLParser {
             SQLJoinTableSource join = new SQLJoinTableSource();
             join.setLeft(tableSource);
             join.setJoinType(joinType);
+            if (asof) {
+                join.setAsof(true);
+            }
 
             boolean isBrace = false;
             if (SQLJoinTableSource.JoinType.COMMA == joinType) {

src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java

@@ -3962,6 +3962,11 @@ public class SQLASTOutputVisitor extends SQLASTVisitorAdapter implements Paramet
         } else {
             println();
 
+            boolean asof = x.isAsof();
+            if (asof) {
+                print0(ucase ? " ASOF ": " asof");
+            }
+
             if (x.isNatural()) {
                 print0(ucase ? "NATURAL " : "natural ");
             }

src/main/java/com/alibaba/druid/util/FnvHash.java

@@ -1115,5 +1115,7 @@ public final class FnvHash {
         long TRANSFORM = fnv1a_64_lower("TRANSFORM");
         long NESTED = fnv1a_64_lower("NESTED");
         long RESTART = fnv1a_64_lower("RESTART");
+
+        long ASOF = fnv1a_64_lower("ASOF");
     }
 }

src/test/java/com/alibaba/druid/bvt/sql/clickhouse/ClickHouseResourceTest.java

@@ -44,6 +44,10 @@ public class ClickHouseResourceTest extends OracleTest {
         exec_test("bvt/parser/clickhouse-1.txt");
     }
 
+    public void test_2() throws Exception {
+        exec_test("bvt/parser/clickhouse-2.txt");
+    }
+
     public void exec_test(String resource) throws Exception {
         System.out.println(resource);
         InputStream is = null;

src/test/resources/bvt/parser/clickhouse-2.txt

@@ -0,0 +1,10 @@
+SELECT expressions_list
+FROM table_1
+ASOF LEFT JOIN table_2
+ON equi_cond AND closest_match_cond
+---------------------------
+SELECT expressions_list
+FROM table_1
+	 ASOF LEFT JOIN table_2
+	ON equi_cond
+		AND closest_match_cond