Read Dynamics NAV Table Metadata with SQL

Question

I would like to be able to read the Dynamics NAV 2013 Table Metadata directly from the SQL Server database without requiring the NAV Development Environment.

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Answer 1

I was able to get an answer for the format of these Metadata binary fields from the author of the deV.ch - man vs. code, Dynamics NAV & C# .NET blog. Based on the reverse engineering by devch, we determined that the first four bytes (32 bits) of these fields are used by NAV to store a "magic number" that determines the custom NAV Blob type.

In the case of these metadata fields, the NAV Compressed Blob-Type magic number is 0x02457d5b (hex). In order to use the standard .Net DeflateStream to Decompress, just throw away those first four magic-number bytes and then process the rest of the stream with DeflateStream as usual.

I was able to successfully test this process with .Net, now I plan to test with Python or some other non-Microsoft deflate tools to see if the deflate implementation follows the industry standard. Thanks again to devch for the article that led to this solution: Accessing Compressed Blobs from outside NAV (NAV2013) (Revisited).

Update: tested with Python zlib and it works! Standards-compliant Deflate algorithm is used once the custom NAV Blob-type magic number is removed. Here's some sample code (Python):

# Example Using Python 3.x
import zlib, sys, struct

# NAV custom Blob-Type identifier (first 4 bytes)
magic = struct.unpack('>I',sys.stdin.buffer.read(4))[0]
print('magic number = %#010x' % magic, file=sys.stderr)
# Remaining binary data is standard DEFLATE without header
input = sys.stdin.buffer.read()
output = zlib.decompress(input,-15)
sys.stdout.buffer.write(output)

Use something like the following to test:

python -u test.py < Input_Meta.blob > Output_Meta.txt

Of course the .Net DeflateStream works after removing the first four bytes as well. This example is just to show that you're not limited to using .Net languages.