Extend the PPL identifier defintion

docs/experiment/ppl/general/identifiers.rst

@@ -23,6 +23,13 @@ Description
 
 A regular identifier is a string of characters that must start with ASCII letter (lower or upper case). The subsequent character can be a combination of letter, digit, underscore (``_``). It cannot be a reversed key word. And whitespace and other special characters are not allowed.
 
+For Elasticsearch, the following identifiers are supported extensionally:
+
+1. Identifiers prefixed by dot ``.``: this is called hidden index in Elasticsearch, for example ``.kibana``.
+2. Identifiers prefixed by at sign ``@``: this is common for meta fields generated in Logstash ingestion.
+3. Identifiers with ``-`` in the middle: this is mostly the case for index name with date information.
+4. Identifiers with star ``*`` present: this is mostly an index pattern for wildcard match.
+
 Examples
 --------
 
@@ -46,12 +53,7 @@ Delimited Identifiers
 Description
 -----------
 
-A delimited identifier is an identifier enclosed in back ticks `````. In this case, the identifier enclosed is not necessarily a regular identifier. In other words, it can contain any special character not allowed by regular identifier. For Elasticsearch, the following identifiers are supported extensionally:
-
-1. Identifiers prefixed by dot ``.``: this is called hidden index in Elasticsearch, for example ``.kibana``.
-2. Identifiers prefixed by at sign ``@``: this is common for meta fields generated in Logstash ingestion.
-3. Identifiers with ``-`` in the middle: this is mostly the case for index name with date information.
-4. Identifiers with star ``*`` present: this is mostly an index pattern for wildcard match.
+A delimited identifier is an identifier enclosed in back ticks `````. In this case, the identifier enclosed is not necessarily a regular identifier. In other words, it can contain any special character not allowed by regular identifier.
 
 Use Cases
 ---------
@@ -67,7 +69,7 @@ Examples
 
 Here are examples for quoting an index name by back ticks::
 
-    od> source=`acc*` | fields `account_number`;
+    od> source=`accounts` | fields `account_number`;
     fetched rows / total rows = 4/4
     +------------------+
     | account_number   |

integ-test/src/test/java/com/amazon/opendistroforelasticsearch/sql/ppl/StatsCommandIT.java

@@ -79,17 +79,18 @@ public void testStatsMax() throws IOException {
   @Test
   public void testStatsNested() throws IOException {
     JSONObject response =
-        executeQuery(String.format("source=%s | stats avg(abs(age)*2) as AGE", TEST_INDEX_ACCOUNT));
+        executeQuery(String.format("source=%s | stats avg(abs(age) * 2) as AGE",
+            TEST_INDEX_ACCOUNT));
     verifySchema(response, schema("AGE", null, "double"));
     verifyDataRows(response, rows(60.342));
   }
 
   @Test
   public void testStatsNestedDoubleValue() throws IOException {
     JSONObject response =
-        executeQuery(String.format("source=%s | stats avg(abs(age)*2.0)",
+        executeQuery(String.format("source=%s | stats avg(abs(age) * 2.0)",
             TEST_INDEX_ACCOUNT));
-    verifySchema(response, schema("avg(abs(age)*2.0)", null, "double"));
+    verifySchema(response, schema("avg(abs(age) * 2.0)", null, "double"));
     verifyDataRows(response, rows(60.342));
   }
 

ppl/src/main/antlr/OpenDistroPPLLexer.g4

@@ -230,13 +230,11 @@ CONCAT_WS:                          'CONCAT_WS';
 LENGTH:                             'LENGTH';
 STRCMP:                             'STRCMP';
 
-// LITERALS AND VALUES
-//STRING_LITERAL:                     DQUOTA_STRING | SQUOTA_STRING | BQUOTA_STRING;
 ID:                                 ID_LITERAL;
 INTEGER_LITERAL:                    DEC_DIGIT+;
 DECIMAL_LITERAL:                    (DEC_DIGIT+)? '.' DEC_DIGIT+;
 
-fragment ID_LITERAL:                [A-Z_]+[A-Z_$0-9@\-]*;
+fragment ID_LITERAL:                [@*A-Z]+?[*A-Z_\-0-9]*;
 DQUOTA_STRING:                      '"' ( '\\'. | '""' | ~('"'| '\\') )* '"';
 SQUOTA_STRING:                      '\'' ('\\'. | '\'\'' | ~('\'' | '\\'))* '\'';
 BQUOTA_STRING:                      '`' ( '\\'. | '``' | ~('`'|'\\'))* '`';

ppl/src/test/java/com/amazon/opendistroforelasticsearch/sql/ppl/parser/AstBuilderTest.java

@@ -50,12 +50,18 @@
 
 import com.amazon.opendistroforelasticsearch.sql.ast.Node;
 import com.amazon.opendistroforelasticsearch.sql.ast.tree.RareTopN.CommandType;
+import com.amazon.opendistroforelasticsearch.sql.common.antlr.SyntaxCheckException;
 import com.amazon.opendistroforelasticsearch.sql.ppl.antlr.PPLSyntaxParser;
 import org.junit.Ignore;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 public class AstBuilderTest {
 
+  @Rule
+  public ExpectedException exceptionRule = ExpectedException.none();
+
   private PPLSyntaxParser parser = new PPLSyntaxParser();
 
   @Test
@@ -366,6 +372,40 @@ public void testIndexName() {
         ));
   }
 
+  @Test
+  public void testIdentifierAsIndexNameStartWithDot() {
+    assertEqual("source=.kibana",
+        relation(".kibana"));
+  }
+
+  @Test
+  public void identifierAsIndexNameWithDotInTheMiddleThrowException() {
+    exceptionRule.expect(SyntaxCheckException.class);
+    plan("source=log.2020.10.10");
+  }
+
+  @Test
+  public void testIdentifierAsIndexNameWithSlashInTheMiddle() {
+    assertEqual("source=log-2020",
+        relation("log-2020"));
+  }
+
+  @Test
+  public void testIdentifierAsIndexNameContainStar() {
+    assertEqual("source=log-2020-10-*",
+        relation("log-2020-10-*"));
+  }
+
+  @Test
+  public void testIdentifierAsFieldNameStartWithAt() {
+    assertEqual("source=log-2020 | fields @timestamp",
+        projectWithArg(
+            relation("log-2020"),
+            defaultFieldsArgs(),
+            field("@timestamp")
+        ));
+  }
+
   @Test
   public void testRareCommand() {
     assertEqual("source=t | rare a",