Transform or iterate over json(b) string values

Dmitry Dolgov, reviewed and lightly edited by me.

diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index bf2c91f02ea799b0380a18f8f0dccdcf7dc4e69b..0db37234fc9955b2329d8c93953676621ad52ada 100644 (file)
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -52,6 +52,25 @@ typedef struct OkeysState
    int         sent_count;
 } OkeysState;
 
+/* state for iterate_json_string_values function */
+typedef struct IterateJsonStringValuesState
+{
+   JsonLexContext                  *lex;
+   JsonIterateStringValuesAction   action;         /* an action that will be applied
+                                                      to each json value */
+   void                            *action_state;  /* any necessary context for iteration */
+} IterateJsonStringValuesState;
+
+/* state for transform_json_string_values function */
+typedef struct TransformJsonStringValuesState
+{
+   JsonLexContext                  *lex;
+   StringInfo                      strval;         /* resulting json */
+   JsonTransformStringValuesAction action;         /* an action that will be applied
+                                                      to each json value */
+   void                            *action_state;  /* any necessary context for transformation */
+} TransformJsonStringValuesState;
+
 /* state for json_get* functions */
 typedef struct GetState
 {
@@ -271,6 +290,18 @@ static void setPathArray(JsonbIterator **it, Datum *path_elems,
             int level, Jsonb *newval, uint32 nelems, int op_type);
 static void addJsonbToParseState(JsonbParseState **jbps, Jsonb *jb);
 
+/* function supporting iterate_json_string_values */
+static void iterate_string_values_scalar(void *state, char *token, JsonTokenType tokentype);
+
+/* functions supporting transform_json_string_values */
+static void transform_string_values_object_start(void *state);
+static void transform_string_values_object_end(void *state);
+static void transform_string_values_array_start(void *state);
+static void transform_string_values_array_end(void *state);
+static void transform_string_values_object_field_start(void *state, char *fname, bool isnull);
+static void transform_string_values_array_element_start(void *state, bool isnull);
+static void transform_string_values_scalar(void *state, char *token, JsonTokenType tokentype);
+
 
 /*
  * SQL function json_object_keys
@@ -4130,3 +4161,208 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
        }
    }
 }
+
+/*
+ * Iterate over jsonb string values or elements, and pass them together with an
+ * iteration state to a specified JsonIterateStringValuesAction.
+ */
+void
+iterate_jsonb_string_values(Jsonb *jb, void *state, JsonIterateStringValuesAction action)
+{
+   JsonbIterator       *it;
+   JsonbValue          v;
+   JsonbIteratorToken  type;
+
+   it = JsonbIteratorInit(&jb->root);
+
+   while ((type = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
+   {
+       if ((type == WJB_VALUE || type == WJB_ELEM) && v.type == jbvString)
+       {
+           action(state, v.val.string.val, v.val.string.len);
+       }
+   }
+}
+
+/*
+ * Iterate over json string values or elements, and pass them together with an
+ * iteration state to a specified JsonIterateStringValuesAction.
+ */
+void
+iterate_json_string_values(text *json, void *action_state, JsonIterateStringValuesAction action)
+{
+   JsonLexContext *lex = makeJsonLexContext(json, true);
+   JsonSemAction *sem = palloc0(sizeof(JsonSemAction));
+   IterateJsonStringValuesState   *state = palloc0(sizeof(IterateJsonStringValuesState));
+
+   state->lex = lex;
+   state->action = action;
+   state->action_state = action_state;
+
+   sem->semstate = (void *) state;
+   sem->scalar = iterate_string_values_scalar;
+
+   pg_parse_json(lex, sem);
+}
+
+/*
+ * An auxiliary function for iterate_json_string_values to invoke a specified
+ * JsonIterateStringValuesAction.
+ */
+static void
+iterate_string_values_scalar(void *state, char *token, JsonTokenType tokentype)
+{
+   IterateJsonStringValuesState   *_state = (IterateJsonStringValuesState *) state;
+   if (tokentype == JSON_TOKEN_STRING)
+       (*_state->action) (_state->action_state, token, strlen(token));
+}
+
+/*
+ * Iterate over a jsonb, and apply a specified JsonTransformStringValuesAction
+ * to every string value or element. Any necessary context for a
+ * JsonTransformStringValuesAction can be passed in the action_state variable.
+ * Function returns a copy of an original jsonb object with transformed values.
+ */
+Jsonb *
+transform_jsonb_string_values(Jsonb *jsonb, void *action_state,
+                             JsonTransformStringValuesAction transform_action)
+{
+   JsonbIterator       *it;
+   JsonbValue          v, *res = NULL;
+   JsonbIteratorToken  type;
+   JsonbParseState     *st = NULL;
+   text                *out;
+   bool                is_scalar = false;
+
+   it = JsonbIteratorInit(&jsonb->root);
+   is_scalar = it->isScalar;
+
+   while ((type = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
+   {
+       if ((type == WJB_VALUE || type == WJB_ELEM) && v.type == jbvString)
+       {
+           out = transform_action(action_state, v.val.string.val, v.val.string.len);
+           v.val.string.val = VARDATA_ANY(out);
+           v.val.string.len = VARSIZE_ANY_EXHDR(out);
+           res = pushJsonbValue(&st, type, type < WJB_BEGIN_ARRAY ? &v : NULL);
+       }
+       else
+       {
+           res = pushJsonbValue(&st, type, (type == WJB_KEY ||
+                                            type == WJB_VALUE ||
+                                            type == WJB_ELEM) ? &v : NULL);
+       }
+   }
+
+   if (res->type == jbvArray)
+       res->val.array.rawScalar = is_scalar;
+
+   return JsonbValueToJsonb(res);
+}
+
+/*
+ * Iterate over a json, and apply a specified JsonTransformStringValuesAction
+ * to every string value or element. Any necessary context for a
+ * JsonTransformStringValuesAction can be passed in the action_state variable.
+ * Function returns a StringInfo, which is a copy of an original json with
+ * transformed values.
+ */
+text *
+transform_json_string_values(text *json, void *action_state,
+                            JsonTransformStringValuesAction transform_action)
+{
+   JsonLexContext *lex = makeJsonLexContext(json, true);
+   JsonSemAction *sem = palloc0(sizeof(JsonSemAction));
+   TransformJsonStringValuesState *state = palloc0(sizeof(TransformJsonStringValuesState));
+
+   state->lex = lex;
+   state->strval = makeStringInfo();
+   state->action = transform_action;
+   state->action_state = action_state;
+
+   sem->semstate = (void *) state;
+   sem->scalar = transform_string_values_scalar;
+   sem->object_start = transform_string_values_object_start;
+   sem->object_end = transform_string_values_object_end;
+   sem->array_start = transform_string_values_array_start;
+   sem->array_end = transform_string_values_array_end;
+   sem->scalar = transform_string_values_scalar;
+   sem->array_element_start = transform_string_values_array_element_start;
+   sem->object_field_start = transform_string_values_object_field_start;
+
+   pg_parse_json(lex, sem);
+
+   return cstring_to_text_with_len(state->strval->data, state->strval->len);
+}
+
+/*
+ * Set of auxiliary functions for transform_json_string_values to invoke a
+ * specified JsonTransformStringValuesAction for all values and left everything
+ * else untouched.
+ */
+static void
+transform_string_values_object_start(void *state)
+{
+   TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
+   appendStringInfoCharMacro(_state->strval, '{');
+}
+
+static void
+transform_string_values_object_end(void *state)
+{
+   TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
+   appendStringInfoCharMacro(_state->strval, '}');
+}
+
+static void
+transform_string_values_array_start(void *state)
+{
+   TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
+   appendStringInfoCharMacro(_state->strval, '[');
+}
+
+static void
+transform_string_values_array_end(void *state)
+{
+   TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
+   appendStringInfoCharMacro(_state->strval, ']');
+}
+
+static void
+transform_string_values_object_field_start(void *state, char *fname, bool isnull)
+{
+   TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
+
+   if (_state->strval->data[_state->strval->len - 1] != '{')
+       appendStringInfoCharMacro(_state->strval, ',');
+
+   /*
+    * Unfortunately we don't have the quoted and escaped string any more, so
+    * we have to re-escape it.
+    */
+   escape_json(_state->strval, fname);
+   appendStringInfoCharMacro(_state->strval, ':');
+}
+
+static void
+transform_string_values_array_element_start(void *state, bool isnull)
+{
+   TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
+
+   if (_state->strval->data[_state->strval->len - 1] != '[')
+       appendStringInfoCharMacro(_state->strval, ',');
+}
+
+static void
+transform_string_values_scalar(void *state, char *token, JsonTokenType tokentype)
+{
+   TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
+
+   if (tokentype == JSON_TOKEN_STRING)
+   {
+       text *out = (*_state->action) (_state->action_state, token, strlen(token));
+       escape_json(_state->strval, text_to_cstring(out));
+   }
+   else
+       appendStringInfoString(_state->strval, token);
+}

diff --git a/src/include/utils/jsonapi.h b/src/include/utils/jsonapi.h
index 8f132d732bedf43aaf6992e73c1dd3e09ebaced9..50c29c3a8661183022046d4fc196ee6758e6acb9 100644 (file)
--- a/src/include/utils/jsonapi.h
+++ b/src/include/utils/jsonapi.h
@@ -14,6 +14,7 @@
 #ifndef JSONAPI_H
 #define JSONAPI_H
 
+#include "jsonb.h"
 #include "lib/stringinfo.h"
 
 typedef enum
@@ -131,4 +132,19 @@ extern JsonLexContext *makeJsonLexContextCstringLen(char *json,
  */
 extern bool IsValidJsonNumber(const char *str, int len);
 
+/* an action that will be applied to each value in iterate_json(b)_string_vaues functions */
+typedef void (*JsonIterateStringValuesAction) (void *state, char *elem_value, int elem_len);
+
+/* an action that will be applied to each value in transform_json(b)_string_values functions */
+typedef text * (*JsonTransformStringValuesAction) (void *state, char *elem_value, int elem_len);
+
+extern void iterate_jsonb_string_values(Jsonb *jb, void *state,
+                                       JsonIterateStringValuesAction action);
+extern void iterate_json_string_values(text *json, void *action_state,
+                                      JsonIterateStringValuesAction action);
+extern Jsonb *transform_jsonb_string_values(Jsonb *jsonb, void *action_state,
+                                           JsonTransformStringValuesAction transform_action);
+extern text *transform_json_string_values(text *json, void *action_state,
+                                         JsonTransformStringValuesAction transform_action);
+
 #endif   /* JSONAPI_H */