Add multiple clause and tree level optimizations

Implement optimizations that can be called in parallel or serial.
Optimizations occur mostly in place and result in a logically equivalent
tree when used correctly.

Optimizations
=============

* Sort - sort all statements within a clause tree
* Simplify - apply negation rules to all statements
* Flatten - merge child clauses with parents
* Compact - merge equivalent statements
* Tidy^ - remove zero statements
* Contradictions - zero contradicting statements and clauses
* StrictEquality - zero fuzzy statements when exact statements are within
  clause
* Tighten - combine multiple fuzzy statements to the least (AND) or
  most (OR) restrictive bounds

^: when used incorrectly can turn an invalid clause tree into a valid
one

1 files changed, 18 insertions, 1 deletions

diff --git a/pkg/query/parser.go b/pkg/query/parser.go
index 14cc227..2bfc014 100644
--- a/pkg/query/parser.go
+++ b/pkg/query/parser.go
@@ -28,8 +28,8 @@ type opType int
 const (
 	OP_UNKNOWN opType = iota
 	OP_EQ             // equal
-	OP_AP             // approximate/fuzzy
 	OP_NE             // not equal
+	OP_AP             // approximate/fuzzy
 	OP_LT             // less than
 	OP_LE             // less than or equal
 	OP_GE             // greater than or equal
@@ -122,6 +122,15 @@ func (v DatetimeValue) Compare(other Valuer) int {
 var _ Valuer = StringValue{}
 var _ Valuer = DatetimeValue{}
 
+// Return if OP_EQ behaves like set membership
+func (t catType) IsSet() bool {
+	return t == CAT_TAGS || t == CAT_AUTHOR || t == CAT_LINKS
+}
+
+func (t catType) IsOrdered() bool {
+	return t == CAT_DATE || t == CAT_FILETIME
+}
+
 func (t catType) String() string {
 	switch t {
 	case CAT_TITLE:
@@ -143,6 +152,14 @@ func (t catType) String() string {
 	}
 }
 
+func (t opType) IsFuzzy() bool {
+	return t == OP_AP || t.IsOrder()
+}
+
+func (t opType) IsOrder() bool {
+	return t == OP_LT || t == OP_LE || t == OP_GT || t == OP_GE
+}
+
 func (t opType) String() string {
 	switch t {
 	case OP_EQ: