opt: refactor NormalizeLikeAny

The NormalizeLikeAny rule no longer allocates, memoizes, and interns a
constant string expression for the literal "%" value.

Release note: None

Author: mgartner

pkg/sql/opt/norm/general_funcs.go

@@ -1545,11 +1545,6 @@ func (c *CustomFuncs) IntConst(d *tree.DInt) opt.ScalarExpr {
 	return c.f.ConstructConst(d, types.Int)
 }
 
-// StrConst constructs a Const holding a DString.
-func (c *CustomFuncs) StrConst(d *tree.DString) opt.ScalarExpr {
-	return c.f.ConstructConst(d, types.String)
-}
-
 // StringFromConst extracts a string from a Const expression. It returns the
 // string and a boolean indicating whether the extraction was successful.
 func (c *CustomFuncs) StringFromConst(expr opt.ScalarExpr) (string, bool) {
@@ -1565,14 +1560,13 @@ func (c *CustomFuncs) StringFromConst(expr opt.ScalarExpr) (string, bool) {
 	return "", false
 }
 
-// EqualConstString compares two Const expressions to see if they hold equal string values.
-func (c *CustomFuncs) EqualConstStrings(left, right opt.ScalarExpr) bool {
-	leftStr, okLeft := c.StringFromConst(left)
-	rightStr, okRight := c.StringFromConst(right)
-	if !okLeft || !okRight {
-		return false
+// ConstStringEquals returns true if e is a constant string expression and is
+// equal to other.
+func (c *CustomFuncs) ConstStringEquals(e opt.ScalarExpr, other *tree.DString) bool {
+	if eStr, ok := c.StringFromConst(e); ok {
+		return eStr == string(*other)
 	}
-	return leftStr == rightStr
+	return false
 }
 
 // IsGreaterThan returns true if the first datum compares as greater than the

pkg/sql/opt/norm/rules/select.opt

@@ -534,7 +534,7 @@ $input
                 $left:* &
                     (ExprIsNeverNull $left (NotNullCols $input))
                 $pattern:(Const) &
-                    (EqualConstStrings $pattern (StrConst "%"))
+                    (ConstStringEquals $pattern "%")
             )
         )
         ...