Add jsonpath .min() and .max() item methods

Author: Nikita Glukhov

src/backend/utils/adt/jsonpath.c

@@ -226,6 +226,8 @@ flattenJsonPathParseItem(StringInfo buf, JsonPathParseItem *item,
 		case jpiCeiling:
 		case jpiDouble:
 		case jpiKeyValue:
+		case jpiMin:
+		case jpiMax:
 			break;
 		case jpiSequence:
 			{
@@ -691,6 +693,12 @@ printJsonPathItem(StringInfo buf, JsonPathItem *v, bool inKey, bool printBracket
 			printJsonPathItem(buf, &elem, false, false);
 			appendStringInfoChar(buf, ')');
 			break;
+		case jpiMin:
+			appendBinaryStringInfo(buf, ".min()", 6);
+			break;
+		case jpiMax:
+			appendBinaryStringInfo(buf, ".max()", 6);
+			break;
 		default:
 			elog(ERROR, "Unknown jsonpath item type: %d", v->type);
 	}
@@ -784,6 +792,8 @@ jspInitByBuffer(JsonPathItem *v, char *base, int32 pos)
 		case jpiDouble:
 		case jpiKeyValue:
 		case jpiLast:
+		case jpiMin:
+		case jpiMax:
 			break;
 		case jpiKey:
 		case jpiString:
@@ -929,7 +939,9 @@ jspGetNext(JsonPathItem *v, JsonPathItem *a)
 			v->type == jpiReduce ||
 			v->type == jpiFold ||
 			v->type == jpiFoldl ||
-			v->type == jpiFoldr
+			v->type == jpiFoldr ||
+			v->type == jpiMin ||
+			v->type == jpiMax
 		);
 
 		if (a)

src/backend/utils/adt/jsonpath_exec.c

@@ -2423,6 +2423,73 @@ recursiveExecuteNoUnwrap(JsonPathExecContext *cxt, JsonPathItem *jsp,
 				res = recursiveExecuteNext(cxt, jsp, NULL, result, found, false);
 			}
 			break;
+		case jpiMin:
+		case jpiMax:
+			if (JsonbType(jb) != jbvArray)
+			{
+				if (cxt->lax)
+					res = recursiveExecuteNext(cxt, jsp, NULL, jb, found, true);
+				else
+					res = jperMakeError(ERRCODE_JSON_ARRAY_NOT_FOUND);
+			}
+			else
+			{
+				JsonbValue	jbvElementBuf;
+				JsonbValue *jbvElement;
+				JsonbValue *jbvResult = NULL;
+				JsonbIterator *it = NULL;
+				JsonbIteratorToken tok;
+				int			size = JsonbArraySize(jb);
+				int			i;
+				JsonPathItemType cmpop =
+					jsp->type == jpiMax ? jpiGreater : jpiLess;
+
+				if (jb->type == jbvBinary)
+				{
+					jbvElement = &jbvElementBuf;
+					it = JsonbIteratorInit(jb->val.binary.data);
+					tok = JsonbIteratorNext(&it, &jbvElementBuf, false);
+					if (tok != WJB_BEGIN_ARRAY)
+						elog(ERROR, "unexpected jsonb token at the array start");
+				}
+
+				for (i = 0; i < size; i++)
+				{
+					if (it)
+					{
+						tok = JsonbIteratorNext(&it, jbvElement, true);
+						if (tok != WJB_ELEM)
+							break;
+					}
+					else
+						jbvElement = &jb->val.array.elems[i];
+
+					if (!i)
+					{
+						jbvResult = it ? copyJsonbValue(jbvElement) : jbvElement;
+					}
+					else
+					{
+						res = makeCompare(cmpop, jbvElement, jbvResult);
+
+						if (jperIsError(res))
+							return jperMakeError(ERRCODE_JSON_SCALAR_REQUIRED);
+
+						if (res == jperOk)
+							jbvResult = it ? copyJsonbValue(jbvElement) : jbvElement;
+					}
+				}
+
+				if (!jbvResult)
+				{
+					res = jperNotFound;
+					break;
+				}
+
+				res = recursiveExecuteNext(cxt, jsp, NULL, jbvResult, found,
+										   false);
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized jsonpath item type: %d", jsp->type);
 	}

src/backend/utils/adt/jsonpath_gram.y

@@ -287,6 +287,7 @@ makeItemObject(List *fields)
 %token	<str>		ANY_P STRICT_P LAX_P LAST_P STARTS_P WITH_P LIKE_REGEX_P FLAG_P
 %token	<str>		ABS_P SIZE_P TYPE_P FLOOR_P DOUBLE_P CEILING_P DATETIME_P
 %token	<str>		KEYVALUE_P MAP_P REDUCE_P FOLD_P FOLDL_P FOLDR_P
+%token	<str>		MIN_P MAX_P
 
 %type	<result>	result
 
@@ -529,6 +530,8 @@ key_name:
 	| FOLD_P
 	| FOLDL_P
 	| FOLDR_P
+	| MIN_P
+	| MAX_P
 	;
 
 method:
@@ -539,6 +542,8 @@ method:
 	| DOUBLE_P						{ $$ = jpiDouble; }
 	| CEILING_P						{ $$ = jpiCeiling; }
 	| KEYVALUE_P					{ $$ = jpiKeyValue; }
+	| MIN_P							{ $$ = jpiMin; }
+	| MAX_P							{ $$ = jpiMax; }
 	;
 %%
 

src/backend/utils/adt/jsonpath_scan.l

@@ -274,6 +274,8 @@ static keyword keywords[] = {
 	{ 3, false,	ABS_P,		"abs"},
 	{ 3, false,	LAX_P,		"lax"},
 	{ 3, false,	MAP_P,		"map"},
+	{ 3, false,	MAX_P,		"max"},
+	{ 3, false,	MIN_P,		"min"},
 	{ 4, false,	FLAG_P,		"flag"},
 	{ 4, false,	FOLD_P,		"fold"},
 	{ 4, false,	LAST_P,		"last"},

src/include/utils/jsonpath.h

@@ -93,6 +93,8 @@ typedef enum JsonPathItemType {
 		jpiFold,
 		jpiFoldl,
 		jpiFoldr,
+		jpiMin,
+		jpiMax,
 } JsonPathItemType;
 
 /* XQuery regex mode flags for LIKE_REGEX predicate */

src/test/regress/expected/jsonb_jsonpath.out

@@ -1736,6 +1736,75 @@ select jsonb '[[1, 2], [3, 4, 5], [], [6, 7]]' @* '$.fold($1 + $2.fold($1 + $2,
  1428
 (1 row)
 
+-- extension: min/max item methods
+select jsonb '1' @* 'strict $.min()';
+ERROR:  SQL/JSON array not found
+select jsonb '1' @* 'lax $.min()';
+ ?column? 
+----------
+ 1
+(1 row)
+
+select jsonb '[]' @* '$.min()';
+ ?column? 
+----------
+(0 rows)
+
+select jsonb '[]' @* '$.max()';
+ ?column? 
+----------
+(0 rows)
+
+select jsonb '[null]' @* '$.min()';
+ ?column? 
+----------
+ null
+(1 row)
+
+select jsonb '[null]' @* '$.max()';
+ ?column? 
+----------
+ null
+(1 row)
+
+select jsonb '[1, 2, 3]' @* '$.min()';
+ ?column? 
+----------
+ 1
+(1 row)
+
+select jsonb '[1, 2, 3]' @* '$.max()';
+ ?column? 
+----------
+ 3
+(1 row)
+
+select jsonb '[2, 3, 5, null, 1, 4, null]' @* '$.min()';
+ ?column? 
+----------
+ 1
+(1 row)
+
+select jsonb '[2, 3, 5, null, 1, 4, null]' @* '$.max()';
+ ?column? 
+----------
+ 5
+(1 row)
+
+select jsonb '["aa", null, "a", "bbb"]' @* '$.min()';
+ ?column? 
+----------
+ "a"
+(1 row)
+
+select jsonb '["aa", null, "a", "bbb"]' @* '$.max()';
+ ?column? 
+----------
+ "bbb"
+(1 row)
+
+select jsonb '[1, null, "2"]' @* '$.max()';
+ERROR:  SQL/JSON scalar required
 -- extension: path sequences
 select jsonb '[1,2,3,4,5]' @* '10, 20, $[*], 30';
  ?column? 

src/test/regress/expected/jsonpath.out

@@ -401,6 +401,18 @@ select '$.fold($1 + $2 + @[1], 2 + 3)'::jsonpath;
  $.fold(($"1" + $"2") + @[1], 2 + 3)
 (1 row)
 
+select '$.min().abs() + 5'::jsonpath;
+      jsonpath       
+---------------------
+ ($.min().abs() + 5)
+(1 row)
+
+select '$.max().floor()'::jsonpath;
+    jsonpath     
+-----------------
+ $.max().floor()
+(1 row)
+
 select '$ ? (@ starts with "abc")'::jsonpath;
         jsonpath         
 -------------------------

src/test/regress/sql/jsonb_jsonpath.sql

@@ -390,6 +390,21 @@ select jsonb '[1, 2, 3]' @* '$.foldl([$1, $2], [])';
 select jsonb '[1, 2, 3]' @* '$.foldr([$2, $1], [])';
 select jsonb '[[1, 2], [3, 4, 5], [], [6, 7]]' @* '$.fold($1 + $2.fold($1 + $2, 100), 1000)';
 
+-- extension: min/max item methods
+select jsonb '1' @* 'strict $.min()';
+select jsonb '1' @* 'lax $.min()';
+select jsonb '[]' @* '$.min()';
+select jsonb '[]' @* '$.max()';
+select jsonb '[null]' @* '$.min()';
+select jsonb '[null]' @* '$.max()';
+select jsonb '[1, 2, 3]' @* '$.min()';
+select jsonb '[1, 2, 3]' @* '$.max()';
+select jsonb '[2, 3, 5, null, 1, 4, null]' @* '$.min()';
+select jsonb '[2, 3, 5, null, 1, 4, null]' @* '$.max()';
+select jsonb '["aa", null, "a", "bbb"]' @* '$.min()';
+select jsonb '["aa", null, "a", "bbb"]' @* '$.max()';
+select jsonb '[1, null, "2"]' @* '$.max()';
+
 -- extension: path sequences
 select jsonb '[1,2,3,4,5]' @* '10, 20, $[*], 30';
 select jsonb '[1,2,3,4,5]' @* 'lax    10, 20, $[*].a, 30';

src/test/regress/sql/jsonpath.sql

@@ -71,6 +71,8 @@ select '$.datetime()'::jsonpath;
 select '$.datetime("datetime template")'::jsonpath;
 select '$.reduce($1 + $2 + @[1])'::jsonpath;
 select '$.fold($1 + $2 + @[1], 2 + 3)'::jsonpath;
+select '$.min().abs() + 5'::jsonpath;
+select '$.max().floor()'::jsonpath;
 
 select '$ ? (@ starts with "abc")'::jsonpath;
 select '$ ? (@ starts with $var)'::jsonpath;