Added json_set_value(obj, path, value) which the item at path in obj …

…to the supplied value

Changes

@@ -1,6 +1,7 @@
 Revision history for Postgres extension pg-json
 
 0.0.2  ...
+    - added json_set_value(json, text, json) which sets the value of a json value at a given path
     - added json_concat(json, json) which concatenates two structures and it's operator equivalent ||
 
 0.0.1  Mon Sep 05

pg-json--0.0.2.sql

@@ -24,6 +24,11 @@ CREATE OR REPLACE FUNCTION json_get_value(data json, path text)
     AS '$libdir/pg-json'
     LANGUAGE C IMMUTABLE STRICT;
 
+CREATE OR REPLACE FUNCTION json_set_value(data json, path text, value json)
+    RETURNS json
+    AS '$libdir/pg-json'
+    LANGUAGE C IMMUTABLE STRICT;
+
 CREATE OR REPLACE FUNCTION json_equals(this json, that json)
     RETURNS boolean
     AS '$libdir/pg-json'

pg-json.c

@@ -63,8 +63,6 @@ Datum json_out(PG_FUNCTION_ARGS) {
     PG_RETURN_CSTRING(result);
 }
 
-PG_FUNCTION_INFO_V1(json_get_value);
-
 static json_t *get_value_at_path(json_t *obj, const char *path) {
     long ix = 0, offset = 0;
     json_t *rv = NULL;
@@ -175,6 +173,8 @@ static text *json_t_to_text(json_t *rv) {
     return NULL;
 }
 
+PG_FUNCTION_INFO_V1(json_get_value);
+
 Datum json_get_value(PG_FUNCTION_ARGS)
 {
     Json*   json = (Json *) PG_GETARG_POINTER(0);
@@ -205,6 +205,130 @@ Datum json_get_value(PG_FUNCTION_ARGS)
     PG_RETURN_TEXT_P(t);
 }
 
+PG_FUNCTION_INFO_V1(json_set_value);
+
+static void set_value_at_path(json_t *obj, const char *path, json_t *new_v) {
+    long ix = 0, offset = 0;
+    char *key;
+    const char *orig_path = path;
+
+    if (*path == '[') {
+        if (!json_is_array(obj)) {
+            elog(ERROR, "Object is not an array for path '%s'", path);
+            return;
+        }
+
+        offset = 1;
+        while (isdigit(path[offset])) {
+            offset++;
+        }
+        if (offset == 1) {
+            elog(ERROR, "Missing array index");
+            return;
+        }
+        if (path[offset] != ']') {
+            elog(ERROR, "Invalid path, expected ']' but got '%c'", path[offset]);
+            return;
+        }
+
+        ix = strtol(path + 1, NULL, 10);
+
+        if (ix >= json_array_size(obj)) {
+            elog(ERROR, "Subscript out of range: %d > %d", (int) ix, (int) json_array_size(obj) - 1);
+            return;        
+        }
+
+        if (path[offset + 1] == '\0') {
+            json_array_set(obj, ix, new_v);
+            return;
+        }
+        else {                
+            obj = json_array_get(obj, ix);
+            if (obj == NULL) {
+                return;            
+            }
+            set_value_at_path(obj, path + offset + 1, new_v);
+        }
+    }
+    else {        
+        /* Skip separators */
+        if (*path == '.') { path++; }
+
+        while(path[offset] != '\0' && path[offset] != '[' && path[offset] != '.') {
+            offset++;
+        }
+
+        if (offset == 0) {
+            elog(ERROR, "No key at %s:%d", __FILE__, __LINE__);
+            return;
+        }
+
+        key = calloc(offset + 1, sizeof(char));
+        strncpy(key, path, offset);        
+
+        if (path[offset] == '\0') {
+            if (json_object_set_new(obj, key, new_v) != 0) {
+                elog(ERROR, "Failed to set key '%s'", key);
+                free(key);
+                return;
+            }
+        }
+        else {
+            obj = json_object_get(obj, key);
+            free(key);
+
+            if (obj == NULL) {
+                return;
+            }
+
+            set_value_at_path(obj, path + offset, new_v);
+        }
+    }
+}
+
+Datum json_set_value(PG_FUNCTION_ARGS)
+{
+    Json*       json;
+    size_t      len;
+    json_t*     root;
+    json_t*     sv;
+    char*       str;
+
+    json_error_t error;
+
+    json = (Json *) PG_GETARG_POINTER(0);
+    len = VARSIZE_ANY_EXHDR(json);
+    root = json_loadb(VARDATA(json), len, 0, &error);
+    if (!root) {
+        elog(ERROR, "Failed to parse json: %s", error.text);
+    }
+
+    json = (Json *) PG_GETARG_POINTER(2);
+    len = VARSIZE_ANY_EXHDR(json);
+    sv = json_loadb(VARDATA(json), len, 0, &error);
+    if (!sv) {
+        elog(ERROR, "Failed to parse value: %s", error.text);
+    }
+
+    set_value_at_path(root, (const char *) text_to_cstring(PG_GETARG_TEXT_P(1)), sv);    
+
+    str = json_dumps(root, JSON_COMPACT);
+
+    /* Avoid leaks */
+    json_decref(root);
+    json_decref(sv);
+
+    /* Convert back to a json type */
+    len = strlen(str);
+    json = (Json *) palloc(len + VARHDRSZ);
+    SET_VARSIZE(json, len + VARHDRSZ);
+    memcpy(VARDATA(json), str, len);
+
+    free(str);
+
+    PG_RETURN_POINTER(json);
+}
+
 /* Comparision */
 static int json_compare(Json *ja, Json *jb) {
     size_t  len;

test.sql

@@ -5,6 +5,7 @@ SELECT json_get_value('{"foo": "bar", "quax": "zorg"}','quax') = 'zorg';
 SELECT json_get_value('{"foo": { "quax": "zorg" } }','foo.quax') = 'zorg';
 SELECT json_get_value('{"foo": [{ "quax": "zorg" }] }','foo[0].quax') = 'zorg';
 
+
 -- ~ is the  operator version of json_get_value
 SELECT '{"foo":"bar"}'::json ~ 'foo' = 'bar';
 
@@ -29,3 +30,7 @@ SELECT json_concat('[1, 2, 3]','[4, 5, 6]') = '[1, 2, 3, 4, 5, 6]';
 SELECT '{"a":"b"}'::json || '{"c":"d"}'::json = '{"a":"b","c":"d"}'::json;
 SELECT '[1, 2, 3]'::json || '[4, 5, 6]'::json = '[1, 2, 3, 4, 5, 6]'::json;
 
+-- Setting by path
+SELECT json_equals(json_set_value('{"foo":"bar"}', 'foo', '{"baz":"quax"}'), '{"foo":{"baz":"quax"}}');
+SELECT json_equals(json_set_value('[1,2,3]', '[1]', '[1,2]'), '[1,[1,2],3]');
+SELECT json_equals(json_set_value('{"foo":[1,{"quax":1}]}', 'foo[1].quax', '[1,2]'), '{"foo":[1,{"quax":[1,2]}]}');