1. Andrew Dunstan
  2. pgdevel

Source

pgdevel / src / backend / utils / adt / jsonfuncs.c

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/*-------------------------------------------------------------------------
 *
 * jsonfuncs.c
 *		Functions to process JSON data type.
 *
 * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	  src/backend/utils/adt/jsonfuncs.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <limits.h>

#include "fmgr.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "access/htup_details.h"
#include "catalog/pg_type.h"
#include "lib/stringinfo.h"
#include "mb/pg_wchar.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/json.h"
#include "utils/jsonapi.h"
#include "utils/memutils.h"

/* semantic action functions for json_object_keys */
static void okeys_object_start(void *state);
static void okeys_object_end(void *state);
static void okeys_object_field_start(void *state, char *fname, bool isnull);
static void okeys_array_start(void *state);
static void okeys_array_end(void *state);
static void okeys_scalar(void *state, char *token, JsonTokenType tokentype);

/* semantic action functions for json_get* functions */
static void get_object_start(void *state);
static void get_object_end(void *state);
static void get_object_field_start(void *state, char *fname, bool isnull);
static void get_object_field_end(void *state, char *fname, bool isnull);
static void get_array_start(void *state);
static void get_array_end(void *state);
static void get_array_element_start(void *state, bool isnull);
static void get_array_element_end(void *state, bool isnull);
static void get_scalar(void *state, char *token, JsonTokenType tokentype);
/* common worker function for json_get* functions */
static text *get_worker(char *json, char *field, int elem_index, char **path, 
						int npath, bool normalize_results);

/* semantic action functions for json_array_length */
static void alen_object_start(void *state);
static void alen_array_start(void *state);
static void alen_array_end(void *state);
static void alen_scalar(void *state, char *token, JsonTokenType tokentype);
static void alen_array_element_start(void *state, bool isnull);

typedef enum
{
	JSON_SEARCH_OBJECT = 1,
	JSON_SEARCH_ARRAY,
	JSON_SEARCH_PATH
}	JsonSearch;

/* stats for json_object_keys */
typedef struct
{
	int			lex_level;
	char	  **result;
	int			result_size;
	int			result_count;
	int			sent_count;
}	okeysState, *OkeysState;

/* state for json_get* functions */
typedef struct
{
	JsonLexContext *lex;
	int			lex_level;
	JsonSearch	search_type;
	int			search_index;
	int			array_index;
	char	   *search_term;
	char	   *result_start;
	text	   *tresult;
	bool		result_is_null;
	bool		normalize_results;
	bool		next_scalar;
	char      **path;
	int         npath;
	char      **current_path;
	bool       *pathok;
	int        *array_level_index;
	int        *path_level_index;
}	getState, *GetState;

/* state for json_array_length */
typedef struct
{
	int			lex_level;
	int         count;
}	alenState, *AlenState;



PG_FUNCTION_INFO_V1(json_object_keys);

Datum
json_object_keys(PG_FUNCTION_ARGS)
{
	FuncCallContext *funcctx;
	OkeysState	state;
	int			i;

	if (SRF_IS_FIRSTCALL())
	{
		text	   *json = PG_GETARG_TEXT_P(0);
		char	   *jsonstr = text_to_cstring(json);
		JsonLexContext lex;
		JsonSemAction sem;

		MemoryContext oldcontext;

		funcctx = SRF_FIRSTCALL_INIT();
		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

		state = palloc(sizeof(okeysState));
		sem = palloc0(sizeof(jsonSemAction));

		state->result_size = 256;
		state->result_count = 0;
		state->sent_count = 0;
		state->lex_level = 0;
		state->result = palloc(256 * sizeof(char *));

		sem->semstate = (void *) state;
		sem->object_start = okeys_object_start;
		sem->object_end = okeys_object_end;
		sem->array_start = okeys_array_start;
		sem->array_end = okeys_array_end;
		sem->scalar = okeys_scalar;
		sem->object_field_start = okeys_object_field_start;
		/* remainder are all NULL, courtesy of palloc0 above */

		/* Set up lexing context. */
		lex.input = jsonstr;
		lex.token_terminator = lex.input;
		lex.line_number = 1;
		lex.line_start = jsonstr;
		lex.strval = makeStringInfo();

		pg_parse_json(&lex, sem);
		/* keys are now in state->result */

		pfree(lex.strval->data);
		pfree(lex.strval);
		pfree(sem);

		MemoryContextSwitchTo(oldcontext);
		funcctx->user_fctx = (void *) state;

	}

	funcctx = SRF_PERCALL_SETUP();
	state = (OkeysState) funcctx->user_fctx;

	if (state->sent_count < state->result_count)
	{
		char	   *nxt = state->result[state->sent_count++];

		SRF_RETURN_NEXT(funcctx, CStringGetTextDatum(nxt));
	}

	/* cleanup to reduce or eliminate memory leaks */
	for (i = 0; i < state->result_count; i++)
		pfree(state->result[i]);
	pfree(state->result);
	pfree(state);

	SRF_RETURN_DONE(funcctx);
}

static void
okeys_object_start(void *state)
{
	OkeysState	_state = (OkeysState) state;

	_state->lex_level++;
}

static void
okeys_object_end(void *state)
{
	OkeysState	_state = (OkeysState) state;

	_state->lex_level--;
}

static void
okeys_object_field_start(void *state, char *fname, bool isnull)
{
	OkeysState	_state = (OkeysState) state;

	if (_state->lex_level != 1)
		return;
	if (_state->result_count >= _state->result_size)
	{
		_state->result_size *= 2;
		_state->result =
			repalloc(_state->result, sizeof(char *) * _state->result_size);
	}
	_state->result[_state->result_count++] = pstrdup(fname);
}

static void
okeys_array_start(void *state)
{
	OkeysState	_state = (OkeysState) state;

	_state->lex_level++;
	if (_state->lex_level == 1)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("cannot call json_object_keys on an array")));
}

static void
okeys_array_end(void *state)
{
	OkeysState	_state = (OkeysState) state;

	_state->lex_level--;
}

static void
okeys_scalar(void *state, char *token, JsonTokenType tokentype)
{
	OkeysState	_state = (OkeysState) state;

	if (_state->lex_level == 0)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("cannot call json_object_keys on a scalar")));

}

/*
 * json_get* functions
 * these all use a common worker, just with some slightly
 * different setup options.
 */

PG_FUNCTION_INFO_V1(json_get_ofield);

Datum
json_get_ofield(PG_FUNCTION_ARGS)
{
	text	   *json = PG_GETARG_TEXT_P(0);
	text	   *fname = PG_GETARG_TEXT_P(1);
	char	   *jsonstr = text_to_cstring(json);
	char	   *fnamestr = text_to_cstring(fname);
	text	   *result;

	result = get_worker(jsonstr, fnamestr, -1, NULL, -1, false);

	if (result != NULL)
		PG_RETURN_TEXT_P(result);
	else
		PG_RETURN_NULL();
}

PG_FUNCTION_INFO_V1(json_get_ofield_as_text);

Datum
json_get_ofield_as_text(PG_FUNCTION_ARGS)
{
	text	   *json = PG_GETARG_TEXT_P(0);
	text	   *fname = PG_GETARG_TEXT_P(1);
	char	   *jsonstr = text_to_cstring(json);
	char	   *fnamestr = text_to_cstring(fname);
	text	   *result;

	result = get_worker(jsonstr, fnamestr, -1, NULL, -1, true);
	if (result != NULL)
		PG_RETURN_TEXT_P(result);
	else
		PG_RETURN_NULL();
}

PG_FUNCTION_INFO_V1(json_get_aelem);

Datum
json_get_aelem(PG_FUNCTION_ARGS)
{
	text	   *json = PG_GETARG_TEXT_P(0);
	int			element = PG_GETARG_INT32(1);
	char	   *jsonstr = text_to_cstring(json);
	text	   *result;

	result = get_worker(jsonstr, NULL, element, NULL, -1, false);

	if (result != NULL)
		PG_RETURN_TEXT_P(result);
	else
		PG_RETURN_NULL();
}


PG_FUNCTION_INFO_V1(json_get_aelem_as_text);

Datum
json_get_aelem_as_text(PG_FUNCTION_ARGS)
{
	text	   *json = PG_GETARG_TEXT_P(0);
	int			element = PG_GETARG_INT32(1);
	char	   *jsonstr = text_to_cstring(json);
	text	   *result;

	result = get_worker(jsonstr, NULL, element, NULL, -1, true);

	if (result != NULL)
		PG_RETURN_TEXT_P(result);
	else
		PG_RETURN_NULL();
}


PG_FUNCTION_INFO_V1(json_get_path);

Datum
json_get_path(PG_FUNCTION_ARGS)
{
	text	   *json = PG_GETARG_TEXT_P(0);
	ArrayType  *path = PG_GETARG_ARRAYTYPE_P(1);
	char	   *jsonstr = text_to_cstring(json);
	text	   *result;
    Datum      *pathtext;
    bool       *pathnulls;
    int         npath;
    char      **pathstr;
	int         i;

	if (array_contains_nulls(path))
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("cannot call json_get_path with null elements in path parameter")));


    deconstruct_array(path, TEXTOID, -1, false, 'i',
                      &pathtext, &pathnulls, &npath);
    
    pathstr = palloc(npath * sizeof(char *));

    for (i = 0; i < npath; i++)
	{
		pathstr[i] = TextDatumGetCString(pathtext[i]);
		if (*pathstr[i] == '\0')
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
					 errmsg("cannot call json_get_path with empty elements in path parameter")));
	}

	result = get_worker(jsonstr, NULL, -1, pathstr, npath, false);

	if (result != NULL)
		PG_RETURN_TEXT_P(result);
	else
		PG_RETURN_NULL();
}

static text *
get_worker(char *json, char *field, int elem_index, char **path, int npath, bool normalize_results)
{
	GetState	state;
	JsonLexContext lex;
	JsonSemAction sem;

	state = palloc0(sizeof(getState));
	sem = palloc0(sizeof(jsonSemAction));

	state->lex_level = 0;
	state->lex = &lex;
	state->normalize_results = normalize_results;
	if (field != NULL)
	{
		state->search_type = JSON_SEARCH_OBJECT;
		state->search_term = field;
	}
	else if (path != NULL)
	{
		int i;
		long int ind;
		char *endptr;

		state->search_type = JSON_SEARCH_PATH;
		state->path = path;
		state->npath = npath;
		state->current_path = palloc(sizeof(char *) * npath);
		state->pathok = palloc(sizeof(bool) * npath);
		state->pathok[0] = true;
		state->array_level_index = palloc(sizeof(int) * npath);
		state->path_level_index = palloc(sizeof(int) * npath);
		for (i=0; i < npath; i++)
		{
			ind = strtol(path[i],&endptr,10);
			if (*endptr == '\0' && ind <= INT_MAX && ind >= 0)
				state->path_level_index[i] = (int) ind;
			else
				state->path_level_index[i] = -1;
 		}
	}
	else
	{
		state->search_type = JSON_SEARCH_ARRAY;
		state->search_index = elem_index;
		state->array_index = -1;
	}

	sem->semstate = (void *) state;
	sem->object_start = get_object_start;
	sem->object_end = get_object_end;
	sem->array_start = get_array_start;
	sem->array_end = get_array_end;
	sem->scalar = get_scalar;
	if (field != NULL || path != NULL)
	{
		sem->object_field_start = get_object_field_start;
		sem->object_field_end = get_object_field_end;
	}
	if (field == NULL)
	{
		sem->array_element_start = get_array_element_start;
		sem->array_element_end = get_array_element_end;
	}

	/* Set up lexing context. */
	lex.input = json;
	lex.token_terminator = lex.input;
	lex.line_number = 1;
	lex.line_start = json;
	lex.strval = makeStringInfo();

	pg_parse_json(&lex, sem);

	return state->tresult;
}

static void
get_object_start(void *state)
{
	GetState	_state = (GetState) state;

	_state->lex_level++;
	if (_state->lex_level == 1 && _state->search_type == JSON_SEARCH_ARRAY)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("cannot call json_get(int) on a non-array")));
}

static void
get_object_end(void *state)
{
	GetState	_state = (GetState) state;

	_state->lex_level--;
}

static void
get_object_field_start(void *state, char *fname, bool isnull)
{
	GetState	_state = (GetState) state;
	bool        get_next = false;

	if (_state->lex_level == 1 && _state->search_type == JSON_SEARCH_OBJECT &&
		strcmp(fname, _state->search_term) == 0)
	{
		get_next = true;
	}
	else if (_state->search_type == JSON_SEARCH_PATH && 
			 _state->lex_level <= _state->npath &&_state->pathok[_state->lex_level - 1] 
			 && strcmp(fname, _state->path[_state->lex_level - 1]) == 0)
	{
		if (_state->lex_level < _state->npath)
			_state->pathok[_state->lex_level] = true;

		if (_state->lex_level == _state->npath)
			get_next = true;
	}

	if (get_next)
	{
		if (_state->tresult != NULL || _state->result_start != NULL)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
					 errmsg("field name is not unique in json object")));

		if (_state->normalize_results && _state->lex->token_type == JSON_TOKEN_STRING)
		{
			_state->next_scalar = true;
		}
		else
		{
			_state->result_start = _state->lex->token_start;
		}
	}
}

static void
get_object_field_end(void *state, char *fname, bool isnull)
{
	GetState	_state = (GetState) state;
	bool        get_last = false;

	if (_state->lex_level == 1 && _state->search_type == JSON_SEARCH_OBJECT &&
	 _state->result_start != NULL && strcmp(fname, _state->search_term) == 0)
	{
		get_last = true;
	}
	else if (_state->search_type == JSON_SEARCH_PATH && 
			 _state->lex_level <= _state->npath &&_state->pathok[_state->lex_level - 1] 
			 && strcmp(fname, _state->path[_state->lex_level - 1]) == 0)
	{
		/* done with this field so reset pathok */
		if (_state->lex_level < _state->npath)
			_state->pathok[_state->lex_level] = false;

		if (_state->lex_level == _state->npath)
			get_last = true;
	}

	if (get_last)
	{
		int			len = _state->lex->prev_token_terminator - _state->result_start;

		_state->tresult = cstring_to_text_with_len(_state->result_start, len);
	}
	/* 
	 * don't need to reset _state->result_start b/c we're only returning one datum,
	 * the conditions should not occur more than once, and this lets us check 
	 * cheaply that they don't (see object_field_start() )
	 */
}

static void
get_array_start(void *state)
{
	GetState	_state = (GetState) state;

	_state->lex_level++;
	if (_state->lex_level == 1 && _state->search_type == JSON_SEARCH_OBJECT)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("cannot call json_get(fieldname) on a non-object")));
	else if (_state->search_type == JSON_SEARCH_PATH && 
			 _state->lex_level <= _state->npath)
		_state->array_level_index[_state->lex_level  - 1] = -1;
}

static void
get_array_end(void *state)
{
	GetState	_state = (GetState) state;

	_state->lex_level--;
}

static void
get_array_element_start(void *state, bool isnull)
{
	GetState	_state = (GetState) state;
	bool        get_next = false;

	if (_state->lex_level == 1 && _state->search_type == JSON_SEARCH_ARRAY)
	{
		_state->array_index++;
		if (_state->array_index == _state->search_index)
			get_next = true;
	}
	else if (_state->search_type == JSON_SEARCH_PATH &&  
			 _state->lex_level <= _state->npath && 
			 _state->pathok[_state->lex_level - 1])
	{
		if (++_state->array_level_index[_state->lex_level  - 1] == _state->path_level_index[_state->lex_level  - 1])
		{
			if (_state->lex_level ==  _state->npath)
				get_next = true;
			else 
				_state->pathok[_state->lex_level] = true;
		}
		
	}

	if (get_next)
	{
		if (_state->normalize_results && _state->lex->token_type == JSON_TOKEN_STRING)
			_state->next_scalar = true;
		else
			_state->result_start = _state->lex->token_start;
	}
}

static void
get_array_element_end(void *state, bool isnull)
{
	GetState	_state = (GetState) state;
	bool        get_last = false;

	if (_state->lex_level == 1 && _state->search_type == JSON_SEARCH_ARRAY &&
		_state->array_index == _state->search_index && _state->result_start != NULL)
	{
		get_last = true;
	}
	else if (_state->search_type == JSON_SEARCH_PATH && 
			 _state->lex_level <= _state->npath &&_state->pathok[_state->lex_level - 1] 
			 && _state->array_level_index[_state->lex_level  - 1] == _state->path_level_index[_state->lex_level  - 1])
	{
		/* done with this element so reset pathok */
		if (_state->lex_level < _state->npath)
			_state->pathok[_state->lex_level] = false;

		if (_state->lex_level == _state->npath)
			get_last = true;
	}
	if (get_last)
	{
		int			len = _state->lex->prev_token_terminator - _state->result_start;

		_state->tresult = cstring_to_text_with_len(_state->result_start, len);
	}
}

static void
get_scalar(void *state, char *token, JsonTokenType tokentype)
{
	GetState	_state = (GetState) state;

	if (_state->lex_level == 0 && _state->search_type != JSON_SEARCH_PATH) 
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("cannot call json_get on a scalar")));
	if (_state->next_scalar)
	{
		_state->tresult = cstring_to_text(token);
		_state->next_scalar = false;
	}

}


PG_FUNCTION_INFO_V1(json_array_length);

Datum
json_array_length(PG_FUNCTION_ARGS)
{
	text	   *json = PG_GETARG_TEXT_P(0);
	char	   *jsonstr = text_to_cstring(json);

	AlenState	   state;
	JsonLexContext lex;
	JsonSemAction  sem;

	state = palloc0(sizeof(alenState));
	sem = palloc0(sizeof(jsonSemAction));

	/* palloc0 does this for us */
#if 0	 
	state->lex_level = 0;
	state->count = 0;
#endif

	sem->semstate = (void *) state;
	sem->object_start = alen_object_start;
	sem->array_start = alen_array_start;
	sem->array_end = alen_array_end;
	sem->scalar = alen_scalar;
	sem->array_element_start = alen_array_element_start;

	/* Set up lexing context. */
	lex.input = jsonstr;
	lex.token_terminator = lex.input;
	lex.line_number = 1;
	lex.line_start = jsonstr;
	lex.strval = NULL ; /* just counting, so this is faster */

	pg_parse_json(&lex, sem);

	PG_RETURN_INT32(state->count);
}


static void
alen_array_start(void *state)
{
	AlenState	_state = (AlenState) state;

	_state->lex_level++;
}

static void
alen_array_end(void *state)
{
	AlenState	_state = (AlenState) state;

	_state->lex_level--;
}

static void
alen_object_start(void *state)
{
	AlenState	_state = (AlenState) state;

	if (_state->lex_level == 0)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("cannot call json_array_length on an object")));
}

static void
alen_scalar(void *state, char *token, JsonTokenType tokentype)
{
	AlenState	_state = (AlenState) state;

	if (_state->lex_level == 0)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("cannot call json_array_length on a scalar")));
}

static void
alen_array_element_start(void *state, bool isnull)
{
	AlenState	_state = (AlenState) state;

	if (_state->lex_level == 1)
		_state->count++;
}

/* semantic action functions for json_get* functions */
static void each_object_start(void *state);
static void each_object_end(void *state);
static void each_object_field_start(void *state, char *fname, bool isnull);
static void each_object_field_end(void *state, char *fname, bool isnull);
static void each_array_start(void *state);
static void each_scalar(void *state, char *token, JsonTokenType tokentype);
/* common worker function for json_get* functions */
/*static text *each_worker(char *json, char *field, int elem_index, bool normalize_results); */


typedef struct
{
	JsonLexContext *lex;
	int			lex_level;
    Tuplestorestate *tuple_store;
    TupleDesc   ret_tdesc;
	MemoryContext tmp_cxt;
	char  *result_start;
} eachState, *EachState;


PG_FUNCTION_INFO_V1(json_each);

Datum
json_each(PG_FUNCTION_ARGS)
{

	text	   *json = PG_GETARG_TEXT_P(0);
	char	   *jsonstr = text_to_cstring(json);
	JsonLexContext lex;
	JsonSemAction sem;
	ReturnSetInfo *rsi;
	MemoryContext old_cxt;
	TupleDesc   tupdesc;
	EachState	state;

	state = palloc0(sizeof(eachState));
	sem = palloc0(sizeof(jsonSemAction));

	rsi = (ReturnSetInfo *) fcinfo->resultinfo;

	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
		(rsi->allowedModes & SFRM_Materialize) == 0 ||
		rsi->expectedDesc == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("set-valued function called in context that "
						"cannot accept a set")));


	rsi->returnMode = SFRM_Materialize;

	(void) get_call_result_type(fcinfo, NULL, &tupdesc);

	/* make these in a sufficiently long-lived memory context */
	old_cxt = MemoryContextSwitchTo(rsi->econtext->ecxt_per_query_memory);

	state->ret_tdesc = CreateTupleDescCopy(tupdesc);
	BlessTupleDesc(	state->ret_tdesc);
	state->tuple_store = 
		tuplestore_begin_heap(rsi->allowedModes & SFRM_Materialize_Random,
							  false, work_mem);

	MemoryContextSwitchTo(old_cxt);

	sem->semstate = (void *) state;
	sem->object_start = each_object_start;
	sem->object_end = each_object_end;
	sem->array_start = each_array_start;
	sem->scalar = each_scalar;
	sem->object_field_start = each_object_field_start;
	sem->object_field_end = each_object_field_end;

	/* Set up lexing context. */
	lex.input = jsonstr;
	lex.token_terminator = lex.input;
	lex.line_number = 1;
	lex.line_start = jsonstr;
	lex.strval = makeStringInfo();

	state->lex = &lex;
	state->lex_level = 0;
	state->tmp_cxt = AllocSetContextCreate(CurrentMemoryContext,
                                  "json_each temporary cxt",
                                  ALLOCSET_DEFAULT_MINSIZE,
                                  ALLOCSET_DEFAULT_INITSIZE,
                                  ALLOCSET_DEFAULT_MAXSIZE);

	pg_parse_json(&lex, sem);
	
	rsi->setResult = state->tuple_store;
	rsi->setDesc = state->ret_tdesc;

	PG_RETURN_NULL();
}

static void each_object_start(void *state)
{
	EachState	_state = (EachState) state;

	_state->lex_level++;
}
static void each_object_end(void *state)
{
	EachState	_state = (EachState) state;

	_state->lex_level--;
}
static void each_object_field_start(void *state, char *fname, bool isnull)
{
	EachState	_state = (EachState) state;

	/* save a pointer to where the value starts */
	if (_state->lex_level == 1)
		_state->result_start = _state->lex->token_start;
}

static void each_object_field_end(void *state, char *fname, bool isnull)
{
	EachState	_state = (EachState) state;
	MemoryContext old_cxt;
	int len;
	text *val;
	HeapTuple   tuple;
	Datum values[2];
	static bool nulls[2] = {false,false};

	/* skip over nested objects */
	if (_state->lex_level != 1)
		return;

	/* use the tmp context so we can clean up after each tuple is done */
	old_cxt = MemoryContextSwitchTo(_state->tmp_cxt);

	len = _state->lex->prev_token_terminator - _state->result_start;
	val = cstring_to_text_with_len(_state->result_start, len);

	values[0] = CStringGetTextDatum(fname);
	values[1] = PointerGetDatum(val);

	tuple = heap_form_tuple(_state->ret_tdesc, values, nulls);
	
	tuplestore_puttuple(_state->tuple_store, tuple);

	/* clean up and switch back */
	MemoryContextSwitchTo(old_cxt);
    MemoryContextReset(_state->tmp_cxt);
}

static void each_array_start(void *state)
{
	EachState	_state = (EachState) state;

	if (_state->lex_level == 0)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("cannot call json_each on an array")));
}

static void each_scalar(void *state, char *token, JsonTokenType tokentype)
{
	EachState	_state = (EachState) state;

	if (_state->lex_level == 0)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("cannot call json_each on a scalar")));
}