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adunstanadunstan
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Transform or iterate over json(b) string values
Dmitry Dolgov, reviewed and lightly edited by me.
1 parent 156d388 commit c80b992

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‎src/backend/utils/adt/jsonfuncs.c

Lines changed: 236 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -52,6 +52,25 @@ typedef struct OkeysState
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int sent_count;
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} OkeysState;
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/* state for iterate_json_string_values function */
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typedef struct IterateJsonStringValuesState
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{
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JsonLexContext *lex;
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JsonIterateStringValuesAction action; /* an action that will be applied
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to each json value */
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void *action_state; /* any necessary context for iteration */
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} IterateJsonStringValuesState;
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/* state for transform_json_string_values function */
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typedef struct TransformJsonStringValuesState
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{
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JsonLexContext *lex;
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StringInfo strval; /* resulting json */
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JsonTransformStringValuesAction action; /* an action that will be applied
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to each json value */
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void *action_state; /* any necessary context for transformation */
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} TransformJsonStringValuesState;
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/* state for json_get* functions */
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typedef struct GetState
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{
@@ -271,6 +290,18 @@ static void setPathArray(JsonbIterator **it, Datum *path_elems,
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int level, Jsonb *newval, uint32 nelems, int op_type);
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static void addJsonbToParseState(JsonbParseState **jbps, Jsonb *jb);
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/* function supporting iterate_json_string_values */
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static void iterate_string_values_scalar(void *state, char *token, JsonTokenType tokentype);
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/* functions supporting transform_json_string_values */
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static void transform_string_values_object_start(void *state);
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static void transform_string_values_object_end(void *state);
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static void transform_string_values_array_start(void *state);
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static void transform_string_values_array_end(void *state);
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static void transform_string_values_object_field_start(void *state, char *fname, bool isnull);
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static void transform_string_values_array_element_start(void *state, bool isnull);
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static void transform_string_values_scalar(void *state, char *token, JsonTokenType tokentype);
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274305

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/*
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* SQL function json_object_keys
@@ -4130,3 +4161,208 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
41304161
}
41314162
}
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}
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/*
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* Iterate over jsonb string values or elements, and pass them together with an
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* iteration state to a specified JsonIterateStringValuesAction.
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*/
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void
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iterate_jsonb_string_values(Jsonb *jb, void *state, JsonIterateStringValuesAction action)
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{
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JsonbIterator *it;
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JsonbValue v;
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JsonbIteratorToken type;
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it = JsonbIteratorInit(&jb->root);
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while ((type = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
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{
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if ((type == WJB_VALUE || type == WJB_ELEM) && v.type == jbvString)
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{
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action(state, v.val.string.val, v.val.string.len);
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}
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}
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}
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/*
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* Iterate over json string values or elements, and pass them together with an
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* iteration state to a specified JsonIterateStringValuesAction.
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*/
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void
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iterate_json_string_values(text *json, void *action_state, JsonIterateStringValuesAction action)
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{
4194+
JsonLexContext *lex = makeJsonLexContext(json, true);
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JsonSemAction *sem = palloc0(sizeof(JsonSemAction));
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IterateJsonStringValuesState *state = palloc0(sizeof(IterateJsonStringValuesState));
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state->lex = lex;
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state->action = action;
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state->action_state = action_state;
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sem->semstate = (void *) state;
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sem->scalar = iterate_string_values_scalar;
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pg_parse_json(lex, sem);
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}
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/*
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* An auxiliary function for iterate_json_string_values to invoke a specified
4210+
* JsonIterateStringValuesAction.
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*/
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static void
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iterate_string_values_scalar(void *state, char *token, JsonTokenType tokentype)
4214+
{
4215+
IterateJsonStringValuesState *_state = (IterateJsonStringValuesState *) state;
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if (tokentype == JSON_TOKEN_STRING)
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(*_state->action) (_state->action_state, token, strlen(token));
4218+
}
4219+
4220+
/*
4221+
* Iterate over a jsonb, and apply a specified JsonTransformStringValuesAction
4222+
* to every string value or element. Any necessary context for a
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* JsonTransformStringValuesAction can be passed in the action_state variable.
4224+
* Function returns a copy of an original jsonb object with transformed values.
4225+
*/
4226+
Jsonb *
4227+
transform_jsonb_string_values(Jsonb *jsonb, void *action_state,
4228+
JsonTransformStringValuesAction transform_action)
4229+
{
4230+
JsonbIterator *it;
4231+
JsonbValue v, *res = NULL;
4232+
JsonbIteratorToken type;
4233+
JsonbParseState *st = NULL;
4234+
text *out;
4235+
bool is_scalar = false;
4236+
4237+
it = JsonbIteratorInit(&jsonb->root);
4238+
is_scalar = it->isScalar;
4239+
4240+
while ((type = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
4241+
{
4242+
if ((type == WJB_VALUE || type == WJB_ELEM) && v.type == jbvString)
4243+
{
4244+
out = transform_action(action_state, v.val.string.val, v.val.string.len);
4245+
v.val.string.val = VARDATA_ANY(out);
4246+
v.val.string.len = VARSIZE_ANY_EXHDR(out);
4247+
res = pushJsonbValue(&st, type, type < WJB_BEGIN_ARRAY ? &v : NULL);
4248+
}
4249+
else
4250+
{
4251+
res = pushJsonbValue(&st, type, (type == WJB_KEY ||
4252+
type == WJB_VALUE ||
4253+
type == WJB_ELEM) ? &v : NULL);
4254+
}
4255+
}
4256+
4257+
if (res->type == jbvArray)
4258+
res->val.array.rawScalar = is_scalar;
4259+
4260+
return JsonbValueToJsonb(res);
4261+
}
4262+
4263+
/*
4264+
* Iterate over a json, and apply a specified JsonTransformStringValuesAction
4265+
* to every string value or element. Any necessary context for a
4266+
* JsonTransformStringValuesAction can be passed in the action_state variable.
4267+
* Function returns a StringInfo, which is a copy of an original json with
4268+
* transformed values.
4269+
*/
4270+
text *
4271+
transform_json_string_values(text *json, void *action_state,
4272+
JsonTransformStringValuesAction transform_action)
4273+
{
4274+
JsonLexContext *lex = makeJsonLexContext(json, true);
4275+
JsonSemAction *sem = palloc0(sizeof(JsonSemAction));
4276+
TransformJsonStringValuesState *state = palloc0(sizeof(TransformJsonStringValuesState));
4277+
4278+
state->lex = lex;
4279+
state->strval = makeStringInfo();
4280+
state->action = transform_action;
4281+
state->action_state = action_state;
4282+
4283+
sem->semstate = (void *) state;
4284+
sem->scalar = transform_string_values_scalar;
4285+
sem->object_start = transform_string_values_object_start;
4286+
sem->object_end = transform_string_values_object_end;
4287+
sem->array_start = transform_string_values_array_start;
4288+
sem->array_end = transform_string_values_array_end;
4289+
sem->scalar = transform_string_values_scalar;
4290+
sem->array_element_start = transform_string_values_array_element_start;
4291+
sem->object_field_start = transform_string_values_object_field_start;
4292+
4293+
pg_parse_json(lex, sem);
4294+
4295+
return cstring_to_text_with_len(state->strval->data, state->strval->len);
4296+
}
4297+
4298+
/*
4299+
* Set of auxiliary functions for transform_json_string_values to invoke a
4300+
* specified JsonTransformStringValuesAction for all values and left everything
4301+
* else untouched.
4302+
*/
4303+
static void
4304+
transform_string_values_object_start(void *state)
4305+
{
4306+
TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
4307+
appendStringInfoCharMacro(_state->strval, '{');
4308+
}
4309+
4310+
static void
4311+
transform_string_values_object_end(void *state)
4312+
{
4313+
TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
4314+
appendStringInfoCharMacro(_state->strval, '}');
4315+
}
4316+
4317+
static void
4318+
transform_string_values_array_start(void *state)
4319+
{
4320+
TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
4321+
appendStringInfoCharMacro(_state->strval, '[');
4322+
}
4323+
4324+
static void
4325+
transform_string_values_array_end(void *state)
4326+
{
4327+
TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
4328+
appendStringInfoCharMacro(_state->strval, ']');
4329+
}
4330+
4331+
static void
4332+
transform_string_values_object_field_start(void *state, char *fname, bool isnull)
4333+
{
4334+
TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
4335+
4336+
if (_state->strval->data[_state->strval->len - 1] != '{')
4337+
appendStringInfoCharMacro(_state->strval, ',');
4338+
4339+
/*
4340+
* Unfortunately we don't have the quoted and escaped string any more, so
4341+
* we have to re-escape it.
4342+
*/
4343+
escape_json(_state->strval, fname);
4344+
appendStringInfoCharMacro(_state->strval, ':');
4345+
}
4346+
4347+
static void
4348+
transform_string_values_array_element_start(void *state, bool isnull)
4349+
{
4350+
TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
4351+
4352+
if (_state->strval->data[_state->strval->len - 1] != '[')
4353+
appendStringInfoCharMacro(_state->strval, ',');
4354+
}
4355+
4356+
static void
4357+
transform_string_values_scalar(void *state, char *token, JsonTokenType tokentype)
4358+
{
4359+
TransformJsonStringValuesState *_state = (TransformJsonStringValuesState *) state;
4360+
4361+
if (tokentype == JSON_TOKEN_STRING)
4362+
{
4363+
text *out = (*_state->action) (_state->action_state, token, strlen(token));
4364+
escape_json(_state->strval, text_to_cstring(out));
4365+
}
4366+
else
4367+
appendStringInfoString(_state->strval, token);
4368+
}

‎src/include/utils/jsonapi.h

Lines changed: 16 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -14,6 +14,7 @@
1414
#ifndef JSONAPI_H
1515
#define JSONAPI_H
1616

17+
#include "jsonb.h"
1718
#include "lib/stringinfo.h"
1819

1920
typedef enum
@@ -131,4 +132,19 @@ extern JsonLexContext *makeJsonLexContextCstringLen(char *json,
131132
*/
132133
extern bool IsValidJsonNumber(const char *str, int len);
133134

135+
/* an action that will be applied to each value in iterate_json(b)_string_vaues functions */
136+
typedef void (*JsonIterateStringValuesAction) (void *state, char *elem_value, int elem_len);
137+
138+
/* an action that will be applied to each value in transform_json(b)_string_values functions */
139+
typedef text * (*JsonTransformStringValuesAction) (void *state, char *elem_value, int elem_len);
140+
141+
extern void iterate_jsonb_string_values(Jsonb *jb, void *state,
142+
JsonIterateStringValuesAction action);
143+
extern void iterate_json_string_values(text *json, void *action_state,
144+
JsonIterateStringValuesAction action);
145+
extern Jsonb *transform_jsonb_string_values(Jsonb *jsonb, void *action_state,
146+
JsonTransformStringValuesAction transform_action);
147+
extern text *transform_json_string_values(text *json, void *action_state,
148+
JsonTransformStringValuesAction transform_action);
149+
134150
#endif /* JSONAPI_H */

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