html_url,issue_url,id,node_id,user,user_label,created_at,updated_at,author_association,body,reactions,issue,issue_label,performed_via_github_app
https://github.com/simonw/datasette/issues/1836#issuecomment-1271003212,https://api.github.com/repos/simonw/datasette/issues/1836,1271003212,IC_kwDOBm6k_c5LwfhM,536941,fgregg,2022-10-07T01:52:04Z,2022-10-07T01:52:04Z,CONTRIBUTOR,"and if we try immutable mode, which is how things are opened by `datasette inspect` we duplicate the files!!!

```python
# test_sql_immutable.py
import sqlite3
import sys

db_name = sys.argv[1]
conn = sqlite3.connect(f'file:/app/{db_name}?immutable=1', uri=True)
cur = conn.cursor()
cur.execute('select count(*) from filing')
print(cur.fetchone())
```","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",1400374908,docker image is duplicating db files somehow,
https://github.com/simonw/datasette/issues/1836#issuecomment-1270992795,https://api.github.com/repos/simonw/datasette/issues/1836,1270992795,IC_kwDOBm6k_c5Lwc-b,536941,fgregg,2022-10-07T01:29:15Z,2022-10-07T01:50:14Z,CONTRIBUTOR,"fascinatingly, telling python to open sqlite in read only mode makes this layer have a size of 0

```python
# test_sql_ro.py
import sqlite3
import sys

db_name = sys.argv[1]
conn = sqlite3.connect(f'file:/app/{db_name}?mode=ro', uri=True)
cur = conn.cursor()
cur.execute('select count(*) from filing')
print(cur.fetchone())
```

that's quite weird because setting the file permissions to read only didn't do anything. (on reflection, that chmod isn't doing anything because the dockerfile commands are run as root)","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",1400374908,docker image is duplicating db files somehow,
https://github.com/simonw/datasette/issues/1836#issuecomment-1270988081,https://api.github.com/repos/simonw/datasette/issues/1836,1270988081,IC_kwDOBm6k_c5Lwb0x,536941,fgregg,2022-10-07T01:19:01Z,2022-10-07T01:27:35Z,CONTRIBUTOR,"okay, some progress!! running some sql against a database file causes that file to get duplicated even if it doesn't apparently change the file.

make a little test script like this:

```python
# test_sql.py
import sqlite3
import sys

db_name = sys.argv[1]
conn = sqlite3.connect(f'file:/app/{db_name}', uri=True)
cur = conn.cursor()
cur.execute('select count(*) from filing')
print(cur.fetchone())
```

then 

```docker
RUN python test_sql.py nlrb.db
```

produced a layer that's the same size as `nlrb.db`!!

","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",1400374908,docker image is duplicating db files somehow,
https://github.com/simonw/datasette/issues/1836#issuecomment-1270936982,https://api.github.com/repos/simonw/datasette/issues/1836,1270936982,IC_kwDOBm6k_c5LwPWW,536941,fgregg,2022-10-07T00:52:41Z,2022-10-07T00:52:41Z,CONTRIBUTOR,"it's not that the inspect command is somehow changing the db files. if i set them to only read-only, the ""inspect"" layer still has the same very large size.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",1400374908,docker image is duplicating db files somehow,
https://github.com/simonw/datasette/issues/1836#issuecomment-1270923537,https://api.github.com/repos/simonw/datasette/issues/1836,1270923537,IC_kwDOBm6k_c5LwMER,536941,fgregg,2022-10-07T00:46:08Z,2022-10-07T00:46:08Z,CONTRIBUTOR,"i thought it was maybe to do with reading through all the files, but that does not seem to be the case

if i make a little test file like:

```python
# test_read.py
import hashlib
import sys
import pathlib

HASH_BLOCK_SIZE = 1024 * 1024

def inspect_hash(path):
    """"""Calculate the hash of a database, efficiently.""""""
    m = hashlib.sha256()
    with path.open(""rb"") as fp:
        while True:
            data = fp.read(HASH_BLOCK_SIZE)
            if not data:
                break
            m.update(data)

    return m.hexdigest()

inspect_hash(pathlib.Path(sys.argv[1]))
```

then a line in the Dockerfile like

```docker
RUN python test_read.py nlrb.db && echo ""[]"" > /etc/inspect.json
```

just produes a layer of `3B`
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",1400374908,docker image is duplicating db files somehow,