Addition of testing and comments

Signed-off-by: Florent Poinsard <[email protected]>

go/vt/sqlparser/predicate_rewriting.go

@@ -98,10 +98,12 @@ func simplifyNot(expr *NotExpr) (Expr, rewriteState) {
 	return expr, noChange{}
 }
 
-// ExtractINFromOR TODO:
+// ExtractINFromOR rewrites the OR expression into an IN clause.
+// Each side of each ORs has to be an equality comparison expression and the column names have to
+// match for all sides of each comparison.
+// This rewriter takes a query that looks like this WHERE a = 1 and b = 11 or a = 2 and b = 12 or a = 3 and b = 13
+// And rewrite that to WHERE (a, b) IN ((1,11), (2,12), (3,13))
 func ExtractINFromOR(expr *OrExpr) []Expr {
-	// This rewriter takes a query that looks like this WHERE a = 1 and b = 11 or a = 2 and b = 12 or a = 3 and b = 13
-	// And rewrite that to WHERE (a, b) IN ((1,11), (2,12), (3,13))
 	var varNames []*ColName
 	var values []Exprs
 	orSlice := orToSlice(expr)

go/vt/sqlparser/predicate_rewriting_test.go

@@ -140,6 +140,18 @@ func TestRewritePredicate(in *testing.T) {
 		// this has too many OR expressions in it, so we don't even try the CNF rewriting
 		in:       "a = 1 and b = 41 or a = 2 and b = 42 or a = 3 and b = 43 or a = 4 and b = 44 or a = 5 and b = 45 or a = 6 and b = 46",
 		expected: "a = 1 and b = 41 or a = 2 and b = 42 or a = 3 and b = 43 or a = 4 and b = 44 or a = 5 and b = 45 or a = 6 and b = 46",
+	}, {
+		in:       "a = 5 and B or a = 6 and C",
+		expected: "a in (5, 6) and (a = 5 or C) and ((B or a = 6) and (B or C))",
+	}, {
+		in:       "(a = 5 and b = 1 or b = 2 and a = 6)",
+		expected: "(a = 5 or b = 2) and a in (5, 6) and (b in (1, 2) and (b = 1 or a = 6))",
+	}, {
+		in:       "(a in (1,5) and B or C and a = 6)",
+		expected: "(a in (1, 5) or C) and a in (1, 5, 6) and ((B or C) and (B or a = 6))",
+	}, {
+		in:       "(a in (1, 5) and B or C and a in (5, 7))",
+		expected: "(a in (1, 5) or C) and a in (1, 5, 7) and ((B or C) and (B or a in (5, 7)))",
 	}}
 
 	for _, tc := range tests {
@@ -158,30 +170,8 @@ func TestExtractINFromOR(in *testing.T) {
 		in       string
 		expected string
 	}{{
-		in:       "(A and B) or (B and A)",
-		expected: "<nil>",
-	}, {
-		in:       "(a = 5 and B) or A",
-		expected: "<nil>",
-	}, {
-		in:       "a = 5 and B or a = 6 and C",
-		expected: "a in (5, 6)",
-	}, {
-		in:       "(a = 5 and b = 1 or b = 2 and a = 6)",
-		expected: "a in (5, 6) and b in (1, 2)",
-	}, {
-		in:       "(a in (1,5) and B or C and a = 6)",
-		expected: "a in (1, 5, 6)",
-	}, {
-		in:       "(a in (1, 5) and B or C and a in (5, 7))",
-		expected: "a in (1, 5, 7)",
-	}, {
-		in:       "(a = 5 and b = 1 or b = 2 and a = 6 or b = 3 and a = 4)",
-		expected: "<nil>",
-	}, {
-		// this has too many OR expressions in it, so we don't even try the CNF rewriting
-		in:       "a = 1 and b = 41 or a = 2 and b = 42 or a = 3 and b = 43 or a = 4 and b = 44 or a = 5 and b = 45",
-		expected: "toto",
+		in:       "a = 1 and b = 41 or a = 2 and b = 42 or a = 3 and b = 43 or a = 4 and b = 44 or a = 5 and b = 45 or a = 6 and b = 46",
+		expected: "(a, b) in ((1, 41), (2, 42), (3, 43), (4, 44), (5, 45), (6, 46))",
 	}}
 
 	for _, tc := range tests {