Change predecence of phrase operator.

<-> operator now have higher predecence than & (AND) operator. This change
was motivated by unexpected difference of similar queries:
'a & b <-> c'::tsquery and 'b <-> c & a'. Before first query means
(a & b) <-> c and second one - '(b <-> c) & a', now phrase operator evaluates
first.

Per suggestion from Tom Lane 32260.1465402409@sss.pgh.pa.us

Author: feodor

src/backend/utils/adt/tsquery.c

@@ -26,10 +26,10 @@
 /* FTS operator priorities, see ts_type.h */
 const int	tsearch_op_priority[OP_COUNT] =
 {
-	3,							/* OP_NOT */
+	4,							/* OP_NOT */
 	2,							/* OP_AND */
 	1,							/* OP_OR */
-	4							/* OP_PHRASE */
+	3							/* OP_PHRASE */
 };
 
 struct TSQueryParserStateData
@@ -430,6 +430,40 @@ pushStop(TSQueryParserState state)
 
 #define STACKDEPTH	32
 
+typedef struct OperatorElement {
+	int8	op;
+	int16	distance;
+} OperatorElement;
+
+static void
+pushOpStack(OperatorElement *stack, int *lenstack, int8 op, int16 distance)
+{
+	if (*lenstack == STACKDEPTH) /* internal error */
+		elog(ERROR, "tsquery stack too small");
+
+	stack[*lenstack].op = op;
+	stack[*lenstack].distance = distance;
+
+	(*lenstack)++;
+}
+
+static void
+cleanOpStack(TSQueryParserState state,
+		   OperatorElement *stack, int *lenstack, int8 op)
+{
+	int	opPriority = OP_PRIORITY(op);
+
+	while(*lenstack)
+	{
+		if (opPriority > OP_PRIORITY(stack[*lenstack - 1].op))
+			break;
+
+		(*lenstack)--;
+		pushOperator(state, stack[*lenstack].op,
+							stack[*lenstack].distance);
+	}
+}
+
 /*
  * Make polish (prefix) notation of query.
  *
@@ -444,11 +478,7 @@ makepol(TSQueryParserState state,
 	ts_tokentype type;
 	int			lenval = 0;
 	char	   *strval = NULL;
-	struct
-	{
-		int8		op;
-		int16		distance;
-	}			opstack[STACKDEPTH];
+	OperatorElement	opstack[STACKDEPTH];
 	int			lenstack = 0;
 	int16		weight = 0;
 	bool		prefix;
@@ -462,49 +492,16 @@ makepol(TSQueryParserState state,
 		{
 			case PT_VAL:
 				pushval(opaque, state, strval, lenval, weight, prefix);
-				while (lenstack && (opstack[lenstack - 1].op == OP_AND ||
-									opstack[lenstack - 1].op == OP_PHRASE ||
-									opstack[lenstack - 1].op == OP_NOT))
-				{
-					lenstack--;
-					pushOperator(state,
-								 opstack[lenstack].op,
-								 opstack[lenstack].distance);
-				}
 				break;
 			case PT_OPR:
-				if (lenstack && operator == OP_OR)
-					pushOperator(state, OP_OR, 0);
-				else
-				{
-					if (lenstack == STACKDEPTH) /* internal error */
-						elog(ERROR, "tsquery stack too small");
-					opstack[lenstack].op = operator;
-					opstack[lenstack].distance = weight;
-					lenstack++;
-				}
+				cleanOpStack(state, opstack, &lenstack, operator);
+				pushOpStack(opstack, &lenstack, operator, weight);
 				break;
 			case PT_OPEN:
 				makepol(state, pushval, opaque);
-
-				while (lenstack && (opstack[lenstack - 1].op == OP_AND ||
-									opstack[lenstack - 1].op == OP_PHRASE ||
-									opstack[lenstack - 1].op == OP_NOT))
-				{
-					lenstack--;
-					pushOperator(state,
-								 opstack[lenstack].op,
-								 opstack[lenstack].distance);
-				}
 				break;
 			case PT_CLOSE:
-				while (lenstack)
-				{
-					lenstack--;
-					pushOperator(state,
-								 opstack[lenstack].op,
-								 opstack[lenstack].distance);
-				};
+				cleanOpStack(state, opstack, &lenstack, OP_OR /* lowest */);
 				return;
 			case PT_ERR:
 			default:
@@ -514,13 +511,8 @@ makepol(TSQueryParserState state,
 								state->buffer)));
 		}
 	}
-	while (lenstack)
-	{
-		lenstack--;
-		pushOperator(state,
-					 opstack[lenstack].op,
-					 opstack[lenstack].distance);
-	}
+
+	cleanOpStack(state, opstack, &lenstack, OP_OR /* lowest */);
 }
 
 static void
@@ -750,7 +742,7 @@ while( ( (inf)->cur - (inf)->buf ) + (addsize) + 1 >= (inf)->buflen ) \
  * print it in infix (human-readable) form
  */
 static void
-infix(INFIX *in, int parentPriority)
+infix(INFIX *in, int parentPriority, bool rightPhraseOp)
 {
 	/* since this function recurses, it could be driven to stack overflow. */
 	check_stack_depth();
@@ -819,7 +811,7 @@ infix(INFIX *in, int parentPriority)
 	}
 	else if (in->curpol->qoperator.oper == OP_NOT)
 	{
-		int			priority = PRINT_PRIORITY(in->curpol);
+		int			priority = QO_PRIORITY(in->curpol);
 
 		if (priority < parentPriority)
 		{
@@ -833,7 +825,7 @@ infix(INFIX *in, int parentPriority)
 		*(in->cur) = '\0';
 		in->curpol++;
 
-		infix(in, priority);
+		infix(in, priority, false);
 		if (priority < parentPriority)
 		{
 			RESIZEBUF(in, 2);
@@ -844,17 +836,15 @@ infix(INFIX *in, int parentPriority)
 	else
 	{
 		int8		op = in->curpol->qoperator.oper;
-		int			priority = PRINT_PRIORITY(in->curpol);
+		int			priority = QO_PRIORITY(in->curpol);
 		int16		distance = in->curpol->qoperator.distance;
 		INFIX		nrm;
 		bool		needParenthesis = false;
 
 		in->curpol++;
 		if (priority < parentPriority ||
-			(op == OP_PHRASE &&
-			 (priority == parentPriority ||		/* phrases are not
-												 * commutative! */
-			  parentPriority == OP_PRIORITY(OP_AND))))
+			 /* phrase operator depends on order */
+			 (op == OP_PHRASE && rightPhraseOp))
 		{
 			needParenthesis = true;
 			RESIZEBUF(in, 2);
@@ -868,11 +858,11 @@ infix(INFIX *in, int parentPriority)
 		nrm.cur = nrm.buf = (char *) palloc(sizeof(char) * nrm.buflen);
 
 		/* get right operand */
-		infix(&nrm, priority);
+		infix(&nrm, priority, (op == OP_PHRASE));
 
 		/* get & print left operand */
 		in->curpol = nrm.curpol;
-		infix(in, priority);
+		infix(in, priority, false);
 
 		/* print operator & right operand */
 		RESIZEBUF(in, 3 + (2 + 10 /* distance */ ) + (nrm.cur - nrm.buf));
@@ -924,7 +914,7 @@ tsqueryout(PG_FUNCTION_ARGS)
 	nrm.cur = nrm.buf = (char *) palloc(sizeof(char) * nrm.buflen);
 	*(nrm.cur) = '\0';
 	nrm.op = GETOPERAND(query);
-	infix(&nrm, -1 /* lowest priority */ );
+	infix(&nrm, -1 /* lowest priority */, false);
 
 	PG_FREE_IF_COPY(query, 0);
 	PG_RETURN_CSTRING(nrm.buf);
@@ -1151,7 +1141,7 @@ tsquerytree(PG_FUNCTION_ARGS)
 		nrm.cur = nrm.buf = (char *) palloc(sizeof(char) * nrm.buflen);
 		*(nrm.cur) = '\0';
 		nrm.op = GETOPERAND(query);
-		infix(&nrm, true);
+		infix(&nrm, -1, false);
 		res = cstring_to_text_with_len(nrm.buf, nrm.cur - nrm.buf);
 		pfree(q);
 	}

src/backend/utils/adt/tsquery_cleanup.c

@@ -25,11 +25,18 @@ typedef struct NODE
 	QueryItem  *valnode;
 } NODE;
 
-/* Non-operator nodes have fake (but highest) priority */
+/*
+ * To simplify walking on query tree and pushing down of phrase operator
+ * we define some fake priority here: phrase operator has highest priority
+ * of any other operators (and we believe here that OP_PHRASE is a highest
+ * code of operations) and value node has ever highest priority.
+ * Priority values of other operations don't matter until they are less than
+ * phrase operator and value node.
+ */
+#define VALUE_PRIORITY			(OP_COUNT + 1)
 #define NODE_PRIORITY(x) \
 	( ((x)->valnode->qoperator.type == QI_OPR) ? \
-			QO_PRIORITY((x)->valnode) : \
-			TOP_PRIORITY )
+		(x)->valnode->qoperator.oper : VALUE_PRIORITY )
 
 /*
  * make query tree from plain view of query
@@ -416,6 +423,10 @@ normalize_phrase_tree(NODE *node)
 		node->left = normalize_phrase_tree(node->left);
 		node->right = normalize_phrase_tree(node->right);
 
+		/*
+		 * if subtree contains only nodes with higher "priority" then
+		 * we are done. See comment near NODE_PRIORITY()
+		 */
 		if (NODE_PRIORITY(node) <= NODE_PRIORITY(node->right) &&
 			NODE_PRIORITY(node) <= NODE_PRIORITY(node->left))
 			return node;

src/include/tsearch/ts_type.h

@@ -217,33 +217,19 @@ typedef struct
 
 /*
  * Legal values for QueryOperator.operator.
- * They should be ordered by priority! We assume that phrase
- * has highest priority, but this agreement is only
- * for query transformation! That's need to simplify
- * algorithm of query transformation.
  */
 #define OP_NOT			1
 #define OP_AND			2
 #define OP_OR			3
-#define OP_PHRASE		4
+#define OP_PHRASE		4  /* highest code, tsquery_cleanup.c */
 #define OP_COUNT		4
 
 extern const int tsearch_op_priority[OP_COUNT];
 
-#define NOT_PHRASE_P	5		/* OP_PHRASE negation operations must have
-								 * greater priority in order to force infix()
-								 * to surround the whole OP_PHRASE expression
-								 * with parentheses. */
-
-#define TOP_PRIORITY	6		/* highest priority for val nodes */
-
 /* get operation priority  by its code*/
 #define OP_PRIORITY(x)	( tsearch_op_priority[(x) - 1] )
 /* get QueryOperator priority */
 #define QO_PRIORITY(x)	OP_PRIORITY(((QueryOperator *) (x))->oper)
-/* special case: get QueryOperator priority for correct printing !(a <-> b>) */
-#define PRINT_PRIORITY(x) \
-	( (((QueryOperator *) (x))->oper == OP_NOT) ? NOT_PHRASE_P : QO_PRIORITY(x) )
 
 typedef struct
 {

src/test/regress/expected/tsdicts.out

@@ -470,15 +470,15 @@ SELECT to_tsquery('hunspell_tst', 'footballyklubber:b & rebookings:A & sky');
 (1 row)
 
 SELECT to_tsquery('hunspell_tst', 'footballyklubber:b <-> sky');
-                                 to_tsquery                                  
------------------------------------------------------------------------------
- ( 'foot':B <-> 'sky' ) & ( 'ball':B <-> 'sky' ) & ( 'klubber':B <-> 'sky' )
+                           to_tsquery                            
+-----------------------------------------------------------------
+ 'foot':B <-> 'sky' & 'ball':B <-> 'sky' & 'klubber':B <-> 'sky'
 (1 row)
 
 SELECT phraseto_tsquery('hunspell_tst', 'footballyklubber sky');
-                           phraseto_tsquery                            
------------------------------------------------------------------------
- ( 'foot' <-> 'sky' ) & ( 'ball' <-> 'sky' ) & ( 'klubber' <-> 'sky' )
+                     phraseto_tsquery                      
+-----------------------------------------------------------
+ 'foot' <-> 'sky' & 'ball' <-> 'sky' & 'klubber' <-> 'sky'
 (1 row)
 
 -- Test ispell dictionary with hunspell affix with FLAG long in configuration

src/test/regress/expected/tsearch.out

@@ -778,9 +778,9 @@ SELECT to_tsquery('english', 'foo <-> a <-> the <-> bar');
 (1 row)
 
 SELECT phraseto_tsquery('english', 'PostgreSQL can be extended by the user in many ways');
-                           phraseto_tsquery                            
------------------------------------------------------------------------
- ( ( ( 'postgresql' <3> 'extend' ) <3> 'user' ) <2> 'mani' ) <-> 'way'
+                     phraseto_tsquery                      
+-----------------------------------------------------------
+ 'postgresql' <3> 'extend' <3> 'user' <2> 'mani' <-> 'way'
 (1 row)
 
 SELECT ts_rank_cd(to_tsvector('english', '
@@ -1215,15 +1215,15 @@ SELECT ts_rewrite('1 & (2 <-> 3)', 'SELECT keyword, sample FROM test_tsquery'::t
 (1 row)
 
 SELECT ts_rewrite('1 & (2 <2> 3)', 'SELECT keyword, sample FROM test_tsquery'::text );
-      ts_rewrite       
------------------------
- '1' & ( '2' <2> '3' )
+    ts_rewrite     
+-------------------
+ '1' & '2' <2> '3'
 (1 row)
 
 SELECT ts_rewrite('5 <-> (1 & (2 <-> 3))', 'SELECT keyword, sample FROM test_tsquery'::text );
-                  ts_rewrite                   
------------------------------------------------
- ( '5' <-> '1' ) & ( '5' <-> ( '2' <-> '3' ) )
+              ts_rewrite               
+---------------------------------------
+ '5' <-> '1' & '5' <-> ( '2' <-> '3' )
 (1 row)
 
 SELECT ts_rewrite('5 <-> (6 | 8)', 'SELECT keyword, sample FROM test_tsquery'::text );