Fixed error while using PosgreSQL reserved keyword in cursor operations

During the cursor prepare, execution flow for statement is not passed through antlr parser. This causes issue when query contains PosgreSQL reserved keywords. This PR addresses this issue, along with any potential issue with query which is not compatible with PostgreSQL

Task: BABEL-5743

Signed-off-by: Shard Gupta shardga@amazon.com

Author: shardgupta

contrib/babelfishpg_tsql/src/cursor.c

@@ -1449,6 +1449,10 @@ execute_sp_cursoropen_common(int *stmt_handle, int *cursor_handle, const char *s
 	Portal		portal;
 	MemoryContext oldcontext;
 	MemoryContext savedPortalCxt;
+	PLtsql_stmt_execsql *parse_result;
+	PLtsql_function *func;
+	char *stmt_copy;
+	char *tsql_stmt = NULL; /* Use this for potentially modified statement */
 
 	/*
 	 * Connect to SPI manager. should be handled in the same way with
@@ -1468,10 +1472,53 @@ execute_sp_cursoropen_common(int *stmt_handle, int *cursor_handle, const char *s
 
 	if (prepare)
 	{
+		/*
+		 * This entire block is to parse the statement by antlr and use the statement for
+		 * cursor execution. This is necessary in some use case, for example when we have
+		 * PostgreSQL reversed keywords in query which is valid in TSQL.
+		 * Antlr parser will add the quotes at necessary places in query so that Postgres engine
+		 * can resolve this query correctly.
+		 */
+		if (stmt)
+		{
+			/* Copy the original statement, because we don't want to use the resultant query in every case. */
+			stmt_copy = pstrdup(stmt);
+			/* Send to antlr parser */
+			func = pltsql_compile_inline(stmt_copy, NULL);
+
+			/*
+			 * Check the node list of type PLtsql_stmt_type. Cursor only support single statement.
+			 * If there are more than 1 statement we will through the error. func->action-body
+			 * returned by pltsql_compile_inline generally contains two default nodes, PLTSQL_STMT_INIT being first
+			 * and PLTSQL_STMT_RETURN being last. In case of empty statement only PLTSQL_STMT_RETURN node will be present.
+			 * So total number of nodes should be 3 for valid cursor execution. Actual query statement will be at second 
+			 * position of type PLTSQL_STMT_EXECSQL.
+			 *
+			 * This is defensive code, where we only assign the tsql_stmt variable to parsed query,
+			 * if the cmd_type is PLTSQL_STMT_EXECSQL. There might be other types of cmd_type like
+			 * PLTSQL_STMT_EXECSQL (for procedures), for them we will keep the old behavior.
+			 * list length should be checked first before trying to deference second node from the list.
+			 * FIXME:We are handling only PLtsql_stmt_execsql type statement, but TSQL support procedure with
+			 * single statement. We also need to explore all other statement types for completion. 
+			 */
+			if(list_length(func->action->body) == 3 &&
+				((PLtsql_stmt *) lsecond(func->action->body))->cmd_type == PLTSQL_STMT_EXECSQL)
+			{
+				parse_result = (PLtsql_stmt_execsql *) lsecond(func->action->body);
+				tsql_stmt = pstrdup(parse_result->sqlstmt->query);
+			}
+
+			/*Free up function memory as this is not needed anymore */
+			pltsql_free_function_memory(func);
+		}
+
 		/* prepare plan and insert a cursor entry */
-		plan = SPI_prepare_cursor(stmt, nBindParams, boundParamsOidList, cursor_options);
+		plan = SPI_prepare_cursor(tsql_stmt?tsql_stmt:stmt, nBindParams, boundParamsOidList, cursor_options);
 		if (plan == NULL)
 			return 1;			/* procedure failed */
+		/* Free memory if tsql_stmt is not null */
+		if (tsql_stmt)
+			pfree((void *)tsql_stmt);
 
 		if (save_plan)
 		{
@@ -1887,4 +1934,4 @@ reset_cached_cursor(void)
 
 	/* Reset sp_cursor_params. */
 	reset_sp_cursor_params();
-}
+}

test/JDBC/expected/BABEL-SPCURSOR.out

@@ -468,7 +468,28 @@ int#!#int#!#int#!#int#!#int
 ~~END~~
 
 
+# cursor with procedure execution test
+CREATE PROCEDURE p1 AS BEGIN select * from babel_cursor_t1 end
+go
+DECLARE @cursor_handle int;
+	EXEC sp_cursoropen @cursor_handle OUTPUT, N'exec p1', 2, 8193;
+go
+~~ERROR (Code: 33557097)~~
+
+~~ERROR (Message: cannot open CALL query as cursor)~~
+
+
+# cursor with empty statement will result in error
+DECLARE @cursor_handle int;
+	EXEC sp_cursoropen @cursor_handle OUTPUT, N'', 2, 8193;
+go
+~~ERROR (Code: 33557097)~~
+
+~~ERROR (Message: cannot open multi-query plan as cursor)~~
+
+
 DROP TABLE babel_cursor_t1
 DROP TABLE t1812
+DROP PROCEDURE p1
 GO
 

test/JDBC/expected/TestCursorFetchNext.out

@@ -64,6 +64,44 @@ int#!#smallint#!#bigint#!#tinyint#!#bit
 #cursor#!#fetch#!#next
 #cursor#!#fetch#!#afterlast
 #cursor#!#fetch#!#next
+cursor#!#close
+~~SUCCESS~~
+cursor#!#open#!#SELECT a year, b month, c quarter FROM test_cursors_fetch_next#!#TYPE_SCROLL_INSENSITIVE#!#CONCUR_READ_ONLY#!#CLOSE_CURSORS_AT_COMMIT
+~~SUCCESS~~
+cursor#!#fetch#!#next
+~~START~~
+int#!#smallint#!#bigint
+0#!#0#!#0
+~~END~~
+
+cursor#!#fetch#!#first
+~~START~~
+int#!#smallint#!#bigint
+0#!#0#!#0
+~~END~~
+
+cursor#!#fetch#!#next
+~~START~~
+int#!#smallint#!#bigint
+<NULL>#!#<NULL>#!#<NULL>
+~~END~~
+
+cursor#!#fetch#!#last
+~~START~~
+int#!#smallint#!#bigint
+211234#!#9780#!#891372401
+~~END~~
+
+cursor#!#close
+~~SUCCESS~~
+cursor#!#open#!#DECLARE @var INT; select @var = 5; select @var + 1;#!#CONCUR_READ_ONLY#!#CLOSE_CURSORS_AT_COMMIT
+~~SUCCESS~~
+cursor#!#fetch#!#next
+~~START~~
+int
+6
+~~END~~
+
 cursor#!#close
 ~~SUCCESS~~
 DROP TABLE test_cursors_fetch_next

test/JDBC/expected/TestCursorPrepExecFetchNext.out

@@ -69,6 +69,38 @@ int#!#smallint#!#bigint#!#tinyint#!#bit
 #cursor#!#fetch#!#next
 #cursor#!#fetch#!#afterlast
 #cursor#!#fetch#!#next
+cursor#!#close
+~~SUCCESS~~
+cursor#!#open#!#prepst#!#SELECT a year, b month, c quarter from test_cursor_prep_exec_fetch_next#!#TYPE_SCROLL_INSENSITIVE#!#CONCUR_READ_ONLY#!#CLOSE_CURSORS_AT_COMMIT
+~~SUCCESS~~
+cursor#!#fetch#!#next
+~~START~~
+int#!#smallint#!#bigint
+0#!#0#!#0
+~~END~~
+
+cursor#!#fetch#!#first
+~~START~~
+int#!#smallint#!#bigint
+0#!#0#!#0
+~~END~~
+
+cursor#!#fetch#!#next
+~~START~~
+int#!#smallint#!#bigint
+<NULL>#!#<NULL>#!#<NULL>
+~~END~~
+
+cursor#!#close
+~~SUCCESS~~
+cursor#!#open#!#DECLARE @var INT; select @var = 5; select @var + 1;#!#CONCUR_READ_ONLY#!#CLOSE_CURSORS_AT_COMMIT
+~~SUCCESS~~
+cursor#!#fetch#!#next
+~~START~~
+int
+6
+~~END~~
+
 cursor#!#close
 ~~SUCCESS~~
 DROP TABLE test_cursor_prep_exec_fetch_next
@@ -285,4 +317,11 @@ float#!#real#!#money#!#smallmoney
 #cursor#!#fetch#!#next
 cursor#!#close
 ~~SUCCESS~~
+# Cursor with multiple selects should return error
+cursor#!#open#!#prepst#!#SELECT * FROM test_cursor_prep_exec_fetch_next;SELECT a FROM test_cursor_prep_exec_fetch_next#!#TYPE_SCROLL_INSENSITIVE#!#CONCUR_READ_ONLY#!#CLOSE_CURSORS_AT_COMMIT
+~~ERROR (Code: 33557097)~~
+
+~~ERROR (Message: cannot open multi-query plan as cursor)~~
+
+
 DROP TABLE test_cursor_prep_exec_fetch_next

test/JDBC/input/BABEL-SPCURSOR.sql

@@ -225,7 +225,20 @@ exec sp_cursorclose @p2;
 exec sp_cursorunprepare @p1;
 go
 
+# cursor with procedure execution test
+CREATE PROCEDURE p1 AS BEGIN select * from babel_cursor_t1 end
+go
+DECLARE @cursor_handle int;
+	EXEC sp_cursoropen @cursor_handle OUTPUT, N'exec p1', 2, 8193;
+go
+
+# cursor with empty statement will result in error
+DECLARE @cursor_handle int;
+	EXEC sp_cursoropen @cursor_handle OUTPUT, N'', 2, 8193;
+go
+
 DROP TABLE babel_cursor_t1
 DROP TABLE t1812
+DROP PROCEDURE p1
 GO
 

test/JDBC/input/cursors/TestCursorFetchNext.txt

@@ -20,6 +20,15 @@ cursor#!#fetch#!#next
 #cursor#!#fetch#!#afterlast
 #cursor#!#fetch#!#next
 cursor#!#close
+cursor#!#open#!#SELECT a year, b month, c quarter FROM test_cursors_fetch_next#!#TYPE_SCROLL_INSENSITIVE#!#CONCUR_READ_ONLY#!#CLOSE_CURSORS_AT_COMMIT
+cursor#!#fetch#!#next
+cursor#!#fetch#!#first
+cursor#!#fetch#!#next
+cursor#!#fetch#!#last
+cursor#!#close
+cursor#!#open#!#DECLARE @var INT; select @var = 5; select @var + 1;#!#CONCUR_READ_ONLY#!#CLOSE_CURSORS_AT_COMMIT
+cursor#!#fetch#!#next
+cursor#!#close
 DROP TABLE test_cursors_fetch_next
 
 CREATE TABLE test_cursors_fetch_next(a CHAR(30), b VARCHAR(30), c NCHAR(30), d NVARCHAR(30));

test/JDBC/input/cursors/TestCursorPrepExecFetchNext.txt

@@ -23,6 +23,14 @@ cursor#!#fetch#!#next
 #cursor#!#fetch#!#afterlast
 #cursor#!#fetch#!#next
 cursor#!#close
+cursor#!#open#!#prepst#!#SELECT a year, b month, c quarter from test_cursor_prep_exec_fetch_next#!#TYPE_SCROLL_INSENSITIVE#!#CONCUR_READ_ONLY#!#CLOSE_CURSORS_AT_COMMIT
+cursor#!#fetch#!#next
+cursor#!#fetch#!#first
+cursor#!#fetch#!#next
+cursor#!#close
+cursor#!#open#!#DECLARE @var INT; select @var = 5; select @var + 1;#!#CONCUR_READ_ONLY#!#CLOSE_CURSORS_AT_COMMIT
+cursor#!#fetch#!#next
+cursor#!#close
 DROP TABLE test_cursor_prep_exec_fetch_next
 
 CREATE TABLE test_cursor_prep_exec_fetch_next(a CHAR(30), b VARCHAR(30), c NCHAR(30), d NVARCHAR(30));
@@ -94,4 +102,7 @@ cursor#!#fetch#!#next
 #cursor#!#fetch#!#afterlast
 #cursor#!#fetch#!#next
 cursor#!#close
+# Cursor with multiple selects should return error
+cursor#!#open#!#prepst#!#SELECT * FROM test_cursor_prep_exec_fetch_next;SELECT a FROM test_cursor_prep_exec_fetch_next#!#TYPE_SCROLL_INSENSITIVE#!#CONCUR_READ_ONLY#!#CLOSE_CURSORS_AT_COMMIT
+
 DROP TABLE test_cursor_prep_exec_fetch_next