Spark3: Support for EXPLAIN statement

src/sqlfluff/dialects/dialect_ansi.py

@@ -3374,9 +3374,7 @@ class ExplainStatementSegment(BaseSegment):
         Ref("DeleteStatementSegment"),
     )
 
-    match_grammar = StartsWith("EXPLAIN")
-
-    parse_grammar = Sequence(
+    match_grammar = Sequence(
         "EXPLAIN",
         explainable_stmt,
     )

src/sqlfluff/dialects/dialect_postgres.py

@@ -1097,9 +1097,7 @@ class ExplainStatementSegment(BaseSegment):
 
     type = "explain_statement"
 
-    match_grammar = ansi_dialect.get_segment("ExplainStatementSegment").match_grammar
-
-    parse_grammar = Sequence(
+    match_grammar = Sequence(
         "EXPLAIN",
         OneOf(
             Sequence(
@@ -1113,7 +1111,9 @@ class ExplainStatementSegment(BaseSegment):
             Bracketed(Delimited(Ref("ExplainOptionSegment"))),
             optional=True,
         ),
-        ansi_dialect.get_segment("ExplainStatementSegment").explainable_stmt,
+        ansi_dialect.get_segment(
+            "ExplainStatementSegment",
+        ).explainable_stmt,
     )
 
 

src/sqlfluff/dialects/dialect_snowflake.py

@@ -2938,7 +2938,7 @@ class ExplainStatementSegment(
     https://docs.snowflake.com/en/sql-reference/sql/explain.html
     """
 
-    parse_grammar = Sequence(
+    match_grammar = Sequence(
         "EXPLAIN",
         Sequence(
             "USING",

src/sqlfluff/dialects/dialect_spark3.py

@@ -1679,6 +1679,34 @@ class TransformClauseSegment(BaseSegment):
     )
 
 
+@spark3_dialect.segment(replace=True)
+class ExplainStatementSegment(BaseSegment):
+    """An `Explain` statement.
+
+    Enhanced from ANSI dialect to allow for additonal parameters.
+
+    EXPLAIN [ EXTENDED | CODEGEN | COST | FORMATTED ] explainable_stmt
+
+    https://spark.apache.org/docs/latest/sql-ref-syntax-qry-explain.html
+    """
+
+    type = "explain_statement"
+
+    explainable_stmt = Ref("StatementSegment")
+
+    match_grammar = Sequence(
+        "EXPLAIN",
+        OneOf(
+            "EXTENDED",
+            "CODEGEN",
+            "COST",
+            "FORMATTED",
+            optional=True,
+        ),
+        explainable_stmt,
+    )
+
+
 # Auxiliary Statements
 @spark3_dialect.segment()
 class AddExecutablePackage(BaseSegment):

test/fixtures/dialects/spark3/explain.sql

@@ -0,0 +1,63 @@
+EXPLAIN SELECT
+    a,
+    b
+FROM person;
+
+EXPLAIN SELECT TRANSFORM (zip_code, name, age)
+    USING 'cat' AS (a, b, c)
+FROM person
+WHERE zip_code > 94511;
+
+EXPLAIN ALTER DATABASE inventory SET DBPROPERTIES (
+    'Edited-by' = 'John'
+);
+
+EXPLAIN ALTER TABLE student RENAME TO studentinfo;
+
+EXPLAIN ALTER VIEW view_identifier RENAME TO view_identifier;
+
+EXPLAIN CREATE DATABASE IF NOT EXISTS database_name
+COMMENT "database_comment"
+LOCATION "root/database_directory"
+WITH DBPROPERTIES ( "property_name" = "property_value");
+
+EXPLAIN CREATE OR REPLACE TEMPORARY FUNCTION IF NOT EXISTS
+function_name AS "class_name" USING FILE "resource_locations";
+
+EXPLAIN CREATE TABLE student (id INT, student_name STRING, age INT) USING CSV;
+
+EXPLAIN
+CREATE TABLE student (id INT, student_name STRING, age INT)
+STORED AS ORC;
+
+EXPLAIN CREATE TABLE student_dupli LIKE student
+ROW FORMAT DELIMITED FIELDS TERMINATED BY ','
+STORED AS TEXTFILE
+TBLPROPERTIES ('owner' = 'xxxx');
+
+EXPLAIN
+CREATE VIEW experienced_employee_extended
+AS SELECT a
+FROM experienced_employee;
+
+EXPLAIN DROP DATABASE IF EXISTS dbname;
+
+EXPLAIN DROP FUNCTION test_avg;
+
+EXPLAIN USE database_name;
+
+EXPLAIN TRUNCATE TABLE student PARTITION(age = 10);
+
+EXPLAIN MSCK REPAIR TABLE table_identifier ADD PARTITIONS;
+
+EXPLAIN REFRESH TABLE tbl1;
+
+EXPLAIN REFRESH FUNCTION func1;
+
+EXPLAIN LOAD DATA LOCAL INPATH '/user/hive/warehouse/students'
+OVERWRITE INTO TABLE test_load;
+
+EXPLAIN INSERT INTO TABLE students VALUES
+('Amy Smith', '123 Park Ave, San Jose', 111111);
+
+EXPLAIN DROP VIEW IF EXISTS view_identifier;