Support unary '+' operators for strings (babelfish-for-postgresql#3013)

The T-SQL grammar allows an arbitrary number of unary + operators to precede an expression, but PG only supports that for numeric expressions. For string expressions, the + will be parsed fine by the T-SQL ANTLR parser, but these will raise an error in PG. In SQL those unary + string operators may look like they are additional concatenation operators, like: SELECT 'a' ++ 'b'. Expressions such as +++(+++@v)) are also valid syntax according to the T-SQL grammar even though they look unusual. In this fix we remove such unary + operators, which are redundant anyway. However we do not touch numeric constants (e.g. +123) since the +, though still redundant, may have been included for code clarity (e.g. +123 as opposed to -123). Signed-off-by: Rob Verschoor [email protected] Issues Resolved BABEL-1924 Support unary '+' operator for string expressions
robverschoor · Oct 14, 2024 · 8ad86ff · 8ad86ff
1 parent 95dbb0b
commit 8ad86ff
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Showing 9 changed files with 1,347 additions and 7 deletions.
diff --git a/contrib/babelfishpg_tsql/src/tsqlIface.cpp b/contrib/babelfishpg_tsql/src/tsqlIface.cpp
@@ -2499,11 +2499,11 @@ class tsqlBuilder : public tsqlCommonMutator
 	{
 		// Check for comparison operators directly followed by an '@@' variable, like =@@
 		handleAtAtVarInPredicate(ctx);
-	}		
+	}	
 	void exitUnary_op_expr(TSqlParser::Unary_op_exprContext *ctx) override
 	{
 		handleBitNotOperator(ctx);
-	}
+	}		
 	void exitPlus_minus_bit_expr(TSqlParser::Plus_minus_bit_exprContext *ctx) override
 	{
 		handleBitOperators(ctx);
@@ -3217,10 +3217,7 @@ class tsqlMutator : public TSqlParserBaseListener
 		// Check for comparison operators directly followed by an '@@' variable, like =@@
 		handleAtAtVarInPredicate(ctx);
 	}	
-	void exitUnary_op_expr(TSqlParser::Unary_op_exprContext *ctx) override
-	{
-		handleBitNotOperator(ctx);
-	}
+
 	void exitPlus_minus_bit_expr(TSqlParser::Plus_minus_bit_exprContext *ctx) override
 	{
 		handleBitOperators(ctx);
@@ -3229,6 +3226,54 @@ class tsqlMutator : public TSqlParserBaseListener
 	{
 		handleModuloOperator(ctx);
 	}
+
+	void enterUnary_op_expr(TSqlParser::Unary_op_exprContext *ctx) override
+	{
+		/* 
+		 * The T-SQL grammar allows an arbitrary number of unary '+' operators to precede an expression, 
+		 * but PG only supports that for numeric expressions. For string expressions, such a '+' will raise an error in PG.
+		 * In SQL this shows as redundant operators, for example for concatenation: SELECT 'a' ++ 'b'. Expressions
+		 * such as +++(+++@v)) are also valid syntax according to the T-SQL grammar even though they look unusual.
+		 * Here we remove such unary '+' operators, which are redundant anyway. 
+		 * However we do not touch numeric constants (e.g. +123) since the '+', although still redundant, may
+		 * have been included for code clarity (e.g. +123 as opposed to -123).
+		 */
+		std::string op = getFullText(ctx->op);	
+		if (op.front() == '+') {	
+			auto rhsctx = ctx->expression();
+			while (true) {						
+				std::string rhs = getFullText(rhsctx);
+				if (
+					(rhs.front() == '\'') ||    // single-quoted strings
+					(rhs.front() == '"')  ||    // both double-quoted strings and double-quoted identifiers
+					(rhs.front() == '@')  ||    // variables
+					(rhs.front() == '(')  ||    // bracketed expressions			
+					(rhs.front() == '[')  ||    // bracket-delimited identifiers
+					(rhs.front() == '_')  ||    // identifiers starting with an underscore
+					std::isalpha(rhs.front())   // identifiers as well as the N'...' string notation
+				   ) {
+					stream.setText(ctx->op->getStartIndex(), " ");	
+					break;
+				}
+				if (rhs.front() == '+')  {
+					if (dynamic_cast<TSqlParser::Unary_op_exprContext *>(rhsctx)) {
+						TSqlParser::Unary_op_exprContext *uctx = static_cast<TSqlParser::Unary_op_exprContext *>(rhsctx);
+						op = getFullText(uctx->op);	
+						if (op.front() == '+') {
+							rhsctx = uctx->expression();	
+							continue;
+						}
+					}
+				}	
+				break; 
+			}
+		}
+		return;
+	}	
+	void exitUnary_op_expr(TSqlParser::Unary_op_exprContext *ctx) override
+	{
+		handleBitNotOperator(ctx);
+	}
 
 };
 

diff --git a/test/JDBC/expected/unary_plus_op_string-vu-cleanup.out b/test/JDBC/expected/unary_plus_op_string-vu-cleanup.out
@@ -0,0 +1,11 @@
+drop procedure p1_unary_plus_op_string 
+go
+
+drop function f1_unary_plus_op_string 
+go
+
+drop view v1_unary_plus_op_string
+go
+
+drop table t1_unary_plus_op_string
+go
diff --git a/test/JDBC/expected/unary_plus_op_string-vu-prepare.out b/test/JDBC/expected/unary_plus_op_string-vu-prepare.out
@@ -0,0 +1,76 @@
+create table t1_unary_plus_op_string(i int, vc varchar(30))
+go
+
+create view v1_unary_plus_op_string as
+select 'view '+++(+N'value1') + 
++ /*comment*/
+(
++ /*comment*/
++ -- comment +
+(
++
+'value2'))++(+(select 'value3')) as col1,
+1 + -2 as col2,
+1 ++ -2 as col3,
+1 + ~2 as col4,
+1 +++++ ~2 as col5,
+1 ++++ (++++ -2) as col6,
+1 ++++ (++++ ~2) as col7
+go
+
+create procedure p1_unary_plus_op_string 
+as
+declare @v varchar(20) = ' test'
+declare @i int = 1
+declare @d datetime='2024-Jan-01 01:02:03' 
+declare @dc decimal(10,4)=1
+select 'proc '+'line1'
+select 'proc '++'line2'
+select 'proc '++N'line3'
+select 'proc '+++++'line4'
+select 'proc '+++++"line5"
+select 'proc '+
++ /*comment*/
+(
++ /*comment*/
++ -- comment +
+(
++
+"line6"))+++@v
+select 'proc ' ++(++(++(select N'line7')))++(+@v)
+select 'proc ' ++ case when len('a'+++ 'b')=2 then 'true' else 'false' end
+select 'proc line8' where 'x' in (+'x')
+select 'proc line9' where 'x' like +'x'
+set @v = 'x'
+select 'proc line10' where 'x' like (+@v)
+select 'proc line11' where 'x' like +(+(+@v))
+select 'proc line 12 ' ++ vc from t1_unary_plus_op_string order by 1  
+select 'proc line 13 ' ++(+vc) from t1_unary_plus_op_string order by 1
+select 'proc line 14 ' ++ [vc] from t1_unary_plus_op_string order by 1 
+select 1 + @i, 2 + (+@i), 3 ++++(++(+++@i)) 
+select +@d, + (+@d), ++++(++(+++@d))
+select 1 +@dc, 2 + (+@dc), 3 ++++(++(+++@dc))
+select 1 + -2 as expr1
+select 1 ++ -2 as expr2
+select 1 + ~2 as expr3
+select 1 +++++ ~2 as expr4
+select 1 ++++ (++++ -2) as expr5
+select 1 ++++ (++++ ~2) as expr6
+EXECUTE('select ''execimm ''++''line1''')
+EXECUTE('select ''execimm ''++N''line2''')
+EXECUTE('select ''execimm ''++(+(select N''line3''))')
+go
+
+create function f1_unary_plus_op_string (@v varchar(10)) returns varchar(30)
+as
+begin
+declare @s varchar(30)
+set @s = 'func '+++(+N'value1') +
++
+(
++ /*comment*/
++ -- comment +
+(++(select "value2")))++(+@v)
+return @s
+end
+go