[TRAFODION-2772] - retrieve a value from Json string got an error #1439
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core/sql/exp/exp_function.cpp
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| char *rltStr = NULL; | ||
| JsonReturnType ret = json_extract_path_text(&rltStr, op_data[1], 1, op_data[2]); | ||
| char *jsonStr = new(heap) char[len1+1]; | ||
| char *jsonAttr = new(heap) char[len2+1]; |
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I'm wondering if we need to delete jsonStr and jsonAttr after the json_extract_path_text call to avoid unnecessary heap pressure. Though if json_extract_path_text itself does new's on the same heap, we'd get heap fragmentation.
Another approach would be to allocate these on the stack instead, avoiding both concerns:
char jsonStr[len1+1];
char jsonAttr[len2+1];
...
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Since the value of len1 can only be determined when executing the query, we cannot define jsonStr as an Array.
Will release the memory manually.
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But we can! C++ allows dynamically-sized arrays on the stack. Try it!
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Here's an example. Compile this program:
// Demonstrate dynamically-sized arrays on C++ stack
#include <iostream>
using namespace std;
int main(int argc, char * argv[])
{
for (size_t i = 5; i < 10; i++)
{
char temp[i+1];
cout << "sizeof(temp) = " << sizeof(temp) << endl;
}
return 0;
}
When you run it, you'll get this output:
[birdsall@edev08 dynChar]$ ./dynChar.exe
sizeof(temp) = 6
sizeof(temp) = 7
sizeof(temp) = 8
sizeof(temp) = 9
sizeof(temp) = 10
[birdsall@edev08 dynChar]$
…lease memory to heap
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…ing array to replace dynamic memory
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