Remove sqlite3-specific info from main README, make it more storage a…

…gnostic and point to plugin-specific README (ros2#1193)

Signed-off-by: Emerson Knapp <[email protected]>

README.md

@@ -116,31 +116,12 @@ It is recommended to use this feature with the splitting options.
 #### Recording with a storage configuration
 
 Storage configuration can be specified in a YAML file passed through the `--storage-config-file` option.
-This can be used to optimize performance for specific use-cases.
+This can be used to optimize performance for specific use cases.
 
-For the default storage plugin (sqlite3), the file has a following syntax:
-```
-read:
-  pragmas: <list of pragma settings for read-only>
-write:
-  pragmas: <list of pragma settings for read/write>
-```
-
-By default, SQLite settings are significantly optimized for performance.
-This might have consequences of bag data being corrupted after an application or system-level crash.
-This consideration only applies to current bagfile in case bag splitting is on (through `--max-bag-*` parameters).
-If increased crash-caused corruption resistance is necessary, use `resilient` option for `--storage-preset-profile` setting.
-
-Settings are fully exposed to the user and should be applied with understanding.
-Please refer to [documentation of pragmas](https://www.sqlite.org/pragma.html).
-
-An example configuration file could look like this:
+See storage plugin documentation for more detail:
+* [sqlite3](rosbag2_storage_sqlite3/README.md#storage-configuration-file)
+* [mcap](rosbag2_storage_mcap/README.md#writer-configuration)
 
-```
-write:
-  pragmas: ["journal_mode = MEMORY", "synchronous = OFF", "schema.cache_size = 1000", "schema.page_size = 4096"]
-
-```
 
 ### Replaying data
 
@@ -207,7 +188,7 @@ This example notes all fields that can have an effect, with a comment on the req
 ```
 output_bags:
 - uri: /output/bag1  # required
-  storage_id: sqlite3  # required
+  storage_id: ""  # will use the default storage plugin, if unspecified
   max_bagfile_size: 0
   max_bagfile_duration: 0
   storage_preset_profile: ""
@@ -233,7 +214,6 @@ $ ros2 bag convert -i bag1 -i bag2 -o out.yaml
 # out.yaml
 output_bags:
 - uri: merged_bag
-  storage_id: sqlite3
   all: true
 ```
 
@@ -245,10 +225,8 @@ $ ros2 bag convert -i bag1 -o out.yaml
 # out.yaml
 output_bags:
 - uri: split1
-  storage_id: sqlite3
   topics: [/topic1, /topic2]
 - uri: split2
-  storage_id: sqlite3
   topics: [/topic3]
 ```
 
@@ -260,7 +238,6 @@ $ ros2 bag convert -i bag1 -o out.yaml
 # out.yaml
 output_bags:
 - uri: compressed
-  storage_id: sqlite3
   all: true
   compression_mode: file
   compression_format: zstd
@@ -340,20 +317,21 @@ $ ros2 launch record_all.launch.xml
 
 ## Storage format plugin architecture
 
-Looking at the output of the `ros2 bag info` command, we can see a field called `storage id:`.
-rosbag2 specifically was designed to support multiple storage formats.
-This allows a flexible adaptation of various storage formats depending on individual use cases.
-As of now, this repository comes with two storage plugins.
-The first plugin, sqlite3 is chosen by default.
-If not specified otherwise, rosbag2 will store and replay all recorded data in an SQLite3 database.
+Looking at the output of the `ros2 bag info` command, we can see a field `Storage id:`.
+Rosbag2 was designed to support multiple storage formats to adapt to individual use cases.
+This repository provides two storage plugins, `mcap` and `sqlite3`.
+The default is `sqlite3`, which is provided to code by [`rosbag2_storage::get_default_storage_id()`](rosbag2_storage/include/rosbag2_storage/default_storage_id.hpp) and defined in [`default_storage_id.cpp`](rosbag2_storage/src/rosbag2_storage/default_storage_id.cpp#L21)
 
-In order to use a specified (non-default) storage format plugin, rosbag2 has a command line argument for it:
+If not specified otherwise, rosbag2 will write data using the default plugin.
+
+In order to use a specified (non-default) storage format plugin, rosbag2 has a command line argument `--storage`:
 
 ```
-$ ros2 bag <record> | <play> | <info> -s <sqlite3> | <rosbag2_v2> | <custom_plugin>
+$ ros2 bag record --storage <storage_id>
 ```
 
-Have a look at each of the individual plugins for further information.
+Bag reading commands can detect the storage plugin automatically, but if for any reason you want to force a specific plugin to read a bag, you can use the `--storage` option on any `ros2 bag` verb.
+
 
 ## Serialization format plugin architecture
 

rosbag2_storage_sqlite3/README.md

@@ -0,0 +1,31 @@
+# rosbag2_storage_sqlite3
+
+Storage implementation plugin for rosbag2 providing SQLite3 `.db3` files as the bag storage backend.
+
+
+## Storage Configuration File
+
+The `--storage-config-file` option for this plugin takes files in the following format:
+
+```
+read:
+  pragmas: <list of SQLite pragma settings for read-only>
+write:
+  pragmas: <list of SQLite pragma settings for write modes>
+```
+
+By default, SQLite settings are significantly optimized for performance.
+This might have consequences of bag data being corrupted after an application or system-level crash.
+This consideration only applies to current bagfile in case bag splitting is on (through `--max-bag-*` parameters).
+If increased crash-caused corruption resistance is necessary, use `resilient` option for `--storage-preset-profile` setting.
+
+Settings are fully exposed to the user and should be applied with understanding.
+Please refer to [documentation of pragmas](https://www.sqlite.org/pragma.html).
+
+An example configuration file could look like this:
+
+```
+write:
+  pragmas: ["journal_mode = MEMORY", "synchronous = OFF", "schema.cache_size = 1000", "schema.page_size = 4096"]
+
+```