printing JsonbPair values of input JSONB on server side?

"T" == T L <tinlyx@gmail.com> writes:

T> //Problem line!!!
T> // elog(NOTICE, "print_kv_pair(): k = %s, v = %s",
T> ptr-> key.val.string.val, numeric_out(ptr->value.val.numeric));

string.val isn't a C string (notice the "not null terminated" comment in
the structure definition), and you can't call numeric_out like that.
Either of those would crash it.

You could use pnstrdup to get a valid C string, and use
DatumGetCString(DirectFunctionCall1(
numeric_out,
NumericGetDatum(ptr->value.val.numeric)))

to get the numeric value as a C string.

--
Andrew (irc:RhodiumToad)

"T" == T L <tinlyx@gmail.com> writes:

T> //problem lines!!! //either elog crashes pg server
T> char *buf = pnstrdup(ptr->key.val.string.val,
T> ptr-> key.val.string.len);
T> elog(NOTICE, "print_kv_pair(): k = %s",
T> (ptr->key).val.string.val); //debug

It doesn't help to make a null-terminated copy of the string if you're
then just going to try and print the original.

elog(NOTICE, "print_kv_pair(): k = %s", buf);

T> elog(NOTICE, "print_kv_pair(): v = %s",
T> DatumGetCString(DirectFunctionCall1(numeric_out,
T> NumericGetDatum(ptr->value.val.numeric))) ); //debug

That should work, _provided_ that value.type == jbvNumeric - did you
consider checking that first?

--
Andrew (irc:RhodiumToad)

"T" == T L <tinlyx@gmail.com> writes:

T> Below is my test. It prints a strange character instead of "a"; and
T> says that the value isn't numeric.

Yeah, there's plenty else wrong with your code.

Did you look at how JsonbToCStringWorker does it? that looks like the
best example I can find on a quick scan.

--
Andrew (irc:RhodiumToad)

Yeah I'm not sure why you're looping using pointer math, the iterators are
there to provide that service. Another function to check out 'jsonb_each',
other than the set returning function parts, it does what it looks like
your are trying to do.

-Michel

On Mon, Mar 18, 2019 at 4:12 PM Andrew Gierth <andrew@tao11.riddles.org.uk>
wrote:

"T" == T L <tinlyx@gmail.com> writes:

T> Below is my test. It prints a strange character instead of "a"; and
T> says that the value isn't numeric.

Yeah, there's plenty else wrong with your code.

Did you look at how JsonbToCStringWorker does it? that looks like the
best example I can find on a quick scan.

--
Andrew (irc:RhodiumToad)

I need this in my C code on the server side. Any link to the `jsonb_each`
for this? Examples I found in a quick search are on the client side in SQL.

I am just confused about the various jsonb types and how to effectively
extract values and convert between them:

There are Jsonb, JsonbValue (plus the associated JsonbPair ) to begin
with. The ` JsonbToCStringWorker ` example that Andrew pointed out uses
still another "JsonbContainer" type.
But the type I get from "PG_GETARG_JSONB_P" is Jsonb. And it doesn't fit
into " JsonbContainer" or the pointer math about "JsonPair" that I found
online.

What I am struggling with adapting some of the iterator code I saw is how
to delete irrelevant code without breaking it. My use case is very
restricted and handles hstore-like jsonb's.
I don't need or want the code to have the ability to descend into nested
objects or handle arrays etc., as they are invalid input in my case.

I thought the pointer math example I found is easier to adapt, but I
couldn't get a valid "JsonbPair" from the input parameter to feed into the
pointer math.

On Tue, Mar 19, 2019 at 9:50 AM Michel Pelletier <
pelletier.michel@gmail.com> wrote:

Yeah I'm not sure why you're looping using pointer math, the iterators
are there to provide that service. Another function to check out
'jsonb_each', other than the set returning function parts, it does what it
looks like your are trying to do.

-Michel

On Mon, Mar 18, 2019 at 4:12 PM Andrew Gierth <
andrew@tao11.riddles.org.uk> wrote:

"T" == T L <tinlyx@gmail.com> writes:

T> Below is my test. It prints a strange character instead of "a"; and
T> says that the value isn't numeric.

Yeah, there's plenty else wrong with your code.

Did you look at how JsonbToCStringWorker does it? that looks like the
best example I can find on a quick scan.

--
Andrew (irc:RhodiumToad)

jsonb_each is a wrapper around each_worker_jsonb. It produces a row for
every key/value pair in an object.

https://doxygen.postgresql.org/jsonfuncs_8c.html#a7511a3aa3918eb956f3f4211d07bdbb0

the iteration is:

while ((r = JsonbIteratorNext(&it, &v, skipNested)) != WJB_DONE)

On Tue, Mar 19, 2019 at 11:20 AM T L <tinlyx@gmail.com> wrote:

I need this in my C code on the server side. Any link to the `jsonb_each`
for this? Examples I found in a quick search are on the client side in SQL.

I am just confused about the various jsonb types and how to effectively
extract values and convert between them:

There are Jsonb, JsonbValue (plus the associated JsonbPair ) to begin
with. The ` JsonbToCStringWorker ` example that Andrew pointed out uses
still another "JsonbContainer" type.
But the type I get from "PG_GETARG_JSONB_P" is Jsonb. And it doesn't fit
into " JsonbContainer" or the pointer math about "JsonPair" that I found
online.

What I am struggling with adapting some of the iterator code I saw is how
to delete irrelevant code without breaking it. My use case is very
restricted and handles hstore-like jsonb's.
I don't need or want the code to have the ability to descend into nested
objects or handle arrays etc., as they are invalid input in my case.

I thought the pointer math example I found is easier to adapt, but I
couldn't get a valid "JsonbPair" from the input parameter to feed into the
pointer math.

On Tue, Mar 19, 2019 at 9:50 AM Michel Pelletier <
pelletier.michel@gmail.com> wrote:

Yeah I'm not sure why you're looping using pointer math, the iterators
are there to provide that service. Another function to check out
'jsonb_each', other than the set returning function parts, it does what it
looks like your are trying to do.

-Michel

On Mon, Mar 18, 2019 at 4:12 PM Andrew Gierth <
andrew@tao11.riddles.org.uk> wrote:

"T" == T L <tinlyx@gmail.com> writes:

T> Below is my test. It prints a strange character instead of "a"; and
T> says that the value isn't numeric.

Yeah, there's plenty else wrong with your code.

Did you look at how JsonbToCStringWorker does it? that looks like the
best example I can find on a quick scan.

--
Andrew (irc:RhodiumToad)

Thanks a lot for the hint. I've used the iteration style and cleaned up
the code as far as I can.
It now correctly prints the keys and values, but the server crashes near
function return.

Any suggestions?

-- function code --

PG_FUNCTION_INFO_V1(print_kv_pair);
Datum
print_kv_pair(PG_FUNCTION_ARGS)
{
//1. extracting JsonbValue
Jsonb *jb = PG_GETARG_JSONB_P(0);
JsonbIterator *it;
JsonbValue v;
JsonbIteratorToken r;
JsonbParseState *state = NULL;

if (jb == NULL)
PG_RETURN_BOOL(false);

if (!JB_ROOT_IS_OBJECT(jb))
ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("Can only take objects")));

it = JsonbIteratorInit(&jb->root);
r = JsonbIteratorNext(&it, &v, false);
if (r != WJB_BEGIN_OBJECT)
ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("Iterator was not an object")));

//2. iterating through key-value pairs
char *buf;
while ((r = JsonbIteratorNext(&it, &v, true)) != WJB_DONE)
{
switch (r) {
case WJB_KEY:
buf = pnstrdup(v.val.string.val, v.val.string.len);
elog(NOTICE, "print_kv_pair(): k = %s", buf); //debug
break;
case WJB_VALUE:
if (v.type != jbvNumeric) {
ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("value must be numeric")));
}
elog(NOTICE, "print_kv_pair(): v = %s",
DatumGetCString(DirectFunctionCall1(numeric_out,
NumericGetDatum(v.val.numeric))) ); //debug
break;
case WJB_END_OBJECT:
break;
default:
elog(ERROR, "invalid JsonbIteratorNext rc: %d", (int ) r);
}
}
elog(NOTICE, "print_kv_pair(): ok4");

PG_RETURN_BOOL(true);
}

-- output --

=> select print_kv_pair('{"a":1, "b": 2}');
NOTICE: print_kv_pair(): k = a
NOTICE: print_kv_pair(): v = 1
NOTICE: print_kv_pair(): k = b
NOTICE: print_kv_pair(): v = 2
NOTICE: print_kv_pair(): ok4
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
!>

On Tue, Mar 19, 2019 at 2:22 PM Michel Pelletier <
pelletier.michel@gmail.com> wrote:

jsonb_each is a wrapper around each_worker_jsonb. It produces a row for
every key/value pair in an object.

https://doxygen.postgresql.org/jsonfuncs_8c.html#a7511a3aa3918eb956f3f4211d07bdbb0

the iteration is:

while ((r = JsonbIteratorNext(&it, &v, skipNested)) != WJB_DONE)

On Tue, Mar 19, 2019 at 11:20 AM T L <tinlyx@gmail.com> wrote:

I need this in my C code on the server side. Any link to the
`jsonb_each` for this? Examples I found in a quick search are on the client
side in SQL.

I am just confused about the various jsonb types and how to effectively
extract values and convert between them:

There are Jsonb, JsonbValue (plus the associated JsonbPair ) to begin
with. The ` JsonbToCStringWorker ` example that Andrew pointed out uses
still another "JsonbContainer" type.
But the type I get from "PG_GETARG_JSONB_P" is Jsonb. And it doesn't fit
into " JsonbContainer" or the pointer math about "JsonPair" that I found
online.

What I am struggling with adapting some of the iterator code I saw is
how to delete irrelevant code without breaking it. My use case is very
restricted and handles hstore-like jsonb's.
I don't need or want the code to have the ability to descend into nested
objects or handle arrays etc., as they are invalid input in my case.

I thought the pointer math example I found is easier to adapt, but I
couldn't get a valid "JsonbPair" from the input parameter to feed into the
pointer math.

On Tue, Mar 19, 2019 at 9:50 AM Michel Pelletier <
pelletier.michel@gmail.com> wrote:

Yeah I'm not sure why you're looping using pointer math, the iterators
are there to provide that service. Another function to check out
'jsonb_each', other than the set returning function parts, it does what it
looks like your are trying to do.

-Michel

On Mon, Mar 18, 2019 at 4:12 PM Andrew Gierth <
andrew@tao11.riddles.org.uk> wrote:

"T" == T L <tinlyx@gmail.com> writes:

T> Below is my test. It prints a strange character instead of "a"; and
T> says that the value isn't numeric.

Yeah, there's plenty else wrong with your code.

Did you look at how JsonbToCStringWorker does it? that looks like the
best example I can find on a quick scan.

--
Andrew (irc:RhodiumToad)

For server crashes you can't beat gdb in my opinion. It's a challenge but
worth it in the long run to have gdb skills if you're coding in C (or
Python, since pdb shares many of gdb's keybindings).

But just looking at the function I don't see what's immediately wrong,
what's your CREATE FUNCTION statement look like?

On Tue, Mar 19, 2019 at 1:08 PM T L <tinlyx@gmail.com> wrote:

Thanks a lot for the hint. I've used the iteration style and cleaned up
the code as far as I can.
It now correctly prints the keys and values, but the server crashes near
function return.

Any suggestions?

-- function code --

PG_FUNCTION_INFO_V1(print_kv_pair);
Datum
print_kv_pair(PG_FUNCTION_ARGS)
{
//1. extracting JsonbValue
Jsonb *jb = PG_GETARG_JSONB_P(0);
JsonbIterator *it;
JsonbValue v;
JsonbIteratorToken r;
JsonbParseState *state = NULL;

if (jb == NULL)
PG_RETURN_BOOL(false);

if (!JB_ROOT_IS_OBJECT(jb))
ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("Can only take objects")));

it = JsonbIteratorInit(&jb->root);
r = JsonbIteratorNext(&it, &v, false);
if (r != WJB_BEGIN_OBJECT)
ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("Iterator was not an object")));

//2. iterating through key-value pairs
char *buf;
while ((r = JsonbIteratorNext(&it, &v, true)) != WJB_DONE)
{
switch (r) {
case WJB_KEY:
buf = pnstrdup(v.val.string.val, v.val.string.len);
elog(NOTICE, "print_kv_pair(): k = %s", buf); //debug
break;
case WJB_VALUE:
if (v.type != jbvNumeric) {
ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("value must be numeric")));
}
elog(NOTICE, "print_kv_pair(): v = %s",
DatumGetCString(DirectFunctionCall1(numeric_out,
NumericGetDatum(v.val.numeric))) ); //debug
break;
case WJB_END_OBJECT:
break;
default:
elog(ERROR, "invalid JsonbIteratorNext rc: %d", (int ) r);
}
}
elog(NOTICE, "print_kv_pair(): ok4");

PG_RETURN_BOOL(true);
}

-- output --

=> select print_kv_pair('{"a":1, "b": 2}');
NOTICE: print_kv_pair(): k = a
NOTICE: print_kv_pair(): v = 1
NOTICE: print_kv_pair(): k = b
NOTICE: print_kv_pair(): v = 2
NOTICE: print_kv_pair(): ok4
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
!>

On Tue, Mar 19, 2019 at 2:22 PM Michel Pelletier <
pelletier.michel@gmail.com> wrote:

jsonb_each is a wrapper around each_worker_jsonb. It produces a row for
every key/value pair in an object.

https://doxygen.postgresql.org/jsonfuncs_8c.html#a7511a3aa3918eb956f3f4211d07bdbb0

the iteration is:

while ((r = JsonbIteratorNext(&it, &v, skipNested)) != WJB_DONE)

On Tue, Mar 19, 2019 at 11:20 AM T L <tinlyx@gmail.com> wrote:

I need this in my C code on the server side. Any link to the
`jsonb_each` for this? Examples I found in a quick search are on the client
side in SQL.

I am just confused about the various jsonb types and how to effectively
extract values and convert between them:

There are Jsonb, JsonbValue (plus the associated JsonbPair ) to begin
with. The ` JsonbToCStringWorker ` example that Andrew pointed out uses
still another "JsonbContainer" type.
But the type I get from "PG_GETARG_JSONB_P" is Jsonb. And it doesn't
fit into " JsonbContainer" or the pointer math about "JsonPair" that I
found online.

What I am struggling with adapting some of the iterator code I saw is
how to delete irrelevant code without breaking it. My use case is very
restricted and handles hstore-like jsonb's.
I don't need or want the code to have the ability to descend into
nested objects or handle arrays etc., as they are invalid input in my case.

I thought the pointer math example I found is easier to adapt, but I
couldn't get a valid "JsonbPair" from the input parameter to feed into the
pointer math.

On Tue, Mar 19, 2019 at 9:50 AM Michel Pelletier <
pelletier.michel@gmail.com> wrote:

Yeah I'm not sure why you're looping using pointer math, the iterators
are there to provide that service. Another function to check out
'jsonb_each', other than the set returning function parts, it does what it
looks like your are trying to do.

-Michel

On Mon, Mar 18, 2019 at 4:12 PM Andrew Gierth <
andrew@tao11.riddles.org.uk> wrote:

"T" == T L <tinlyx@gmail.com> writes:

T> Below is my test. It prints a strange character instead of "a";
and
T> says that the value isn't numeric.

Yeah, there's plenty else wrong with your code.

Did you look at how JsonbToCStringWorker does it? that looks like the
best example I can find on a quick scan.

--
Andrew (irc:RhodiumToad)

Yeah I'm not sure why you're looping using pointer math, the iterators are
there to provide that service. Another function to check out 'jsonb_each',
other than the set returning function parts, it does what it looks like
your are trying to do.

-Michel

On Mon, Mar 18, 2019 at 4:12 PM Andrew Gierth <andrew@tao11.riddles.org.uk>
wrote:

"T" == T L <tinlyx@gmail.com> writes:

T> Below is my test. It prints a strange character instead of "a"; and
T> says that the value isn't numeric.

Yeah, there's plenty else wrong with your code.

Did you look at how JsonbToCStringWorker does it? that looks like the
best example I can find on a quick scan.

--
Andrew (irc:RhodiumToad)