v.edit: Implement the batch option for batch editing

[HuidaeCho]

This PR implements the new batch option for batch editing of a lot of features. For example, without this option, we need this script to extract the upper halves of roadsmajor from the NC sample dataset,

# in nc_spm_08_grass7/user1

# copy roadsmajor
g.copy vect=roadsmajor,roadsmajor_upper_half_wo_batch

# find road centers
v.db.select map=roadsmajor -c col=cat |
        awk '{printf "P %d %d 50%%\n", $1, $1}' |
        v.segment roadsmajor output=roadsmajor_center

# break roads at their center
v.to.db -p map=roadsmajor_center option=coor sep=comma |
        sed '/^cat/d' |
        while read cat x y; do
        v.edit map=roadsmajor_upper_half_wo_batch tool=break cats=$cat coords=$x,$y
done

# delete lower halves
v.to.db -p map=roadsmajor option=end sep=comma |
        sed '/^cat/d' |
        while read cat x y; do
        v.edit map=roadsmajor_upper_half_wo_batch tool=delete cats=$cat coords=$x,$y
done

It took 11.938 seconds on i9-12900. On the same CPU, with the new option, it took 2.180 seconds:

# in nc_spm_08_grass7/user1

# copy roadsmajor
g.copy vect=roadsmajor,roadsmajor_upper_half_w_batch

# find road centers
v.db.select map=roadsmajor -c col=cat |
        awk '{printf "P %d %d 50%%\n", $1, $1}' |
        v.segment roadsmajor output=roadsmajor_center --o

# create a batch table and pipe it to v.edit
(
# use these batch columns
echo "tool|cats|coords"

# break roads at their center
v.to.db -p map=roadsmajor_center option=coor sep=space |
        awk '!/^cat/{printf "break|%d|%s,%s\n", $1, $2, $3}'

# delete lower halves
v.to.db -p map=roadsmajor option=end sep=space |
        awk '!/^cat/{printf "delete|%d|%s,%s\n", $1, $2, $3}'

# the above three commands produce the following table:
# tool|cats|coords
# break|1|637108.11963224,257241.783755701
# break|2|636792.27198317,254339.365766968
# break|3|638449.758677739,248299.357582029
# ...
# delete|1|637209.083058167,257970.129540226
# delete|2|636981.336042672,256517.602235172
# delete|3|637960.264160529,248293.868427705
# ...
) | v.edit map=roadsmajor_upper_half_w_batch batch=-

Red is the upper halves.

[HuidaeCho]

This is for a separate PR?

grass/vector/v.edit/main.c

Lines 473 to 478 in 87d2d42

	/* build topology only if requested or if tool!=select */
	if (action_mode != MODE_SELECT && action_mode != MODE_NONE &&
	params.topo->answer != 1) {
	Vect_build_partial(&Map, GV_BUILD_NONE);
	Vect_build(&Map);
	}

I think we need && ret > 0 check to avoid building topology unnecessarily when there were no edits.

[HuidaeCho]

@HuidaeCho I tested the new separator parameter, everything works as expected. I just have little comment on running v.edit on a file with different separator than used in input file:

head -n2 /tmp/batch 
tool,cats,coords
break,1,"637108.11963224,257241.783755701"

v.edit map=roadsmajor_upper_half batch=/tmp/batch 
ERROR: Unknown batch column 'tool,cats,coords' in line 1

v.edit map=roadsmajor_upper_half batch=/tmp/batch sep=,
ERROR: Unable to open vector map <roadsmajor_upper_half> on topological
       level. Try to rebuild vector topology by v.build.

Please try it again.

[HuidaeCho]

This is for a separate PR?

grass/vector/v.edit/main.c

Lines 473 to 478 in 87d2d42

	/* build topology only if requested or if tool!=select */
	if (action_mode != MODE_SELECT && action_mode != MODE_NONE &&
	params.topo->answer != 1) {
	Vect_build_partial(&Map, GV_BUILD_NONE);
	Vect_build(&Map);
	}

I think we need && ret > 0 check to avoid building topology unnecessarily when there were no edits.

I was wrong. Level 2 vector always requires topology building to remain level 2 even if there are no changes. Just tried this:

Vect_open_update2();
/* do nothing */
Vect_close();

Level 2 vector became level 1. I'm not sure why and how...

[metzm]

I was wrong. Level 2 vector always requires topology building to remain level 2 even if there are no changes. Just tried this:

Vect_open_update2();
/* do nothing */
Vect_close();

Level 2 vector became level 1. I'm not sure why and how...

Please try #3459. If this works for you, you are welcome to include this single line in your PR and I close mine without merging.

[HuidaeCho]

Also, JSON streaming is something we need to consider for large data streaming. e.g., one edit (object) per line. Does JSON have the standard format for this? If this is not somehow supported, JSON data will need to be generated completely before we can start editing any features. Another consideration is its data size (almost twice 556 bytes vs. 270 bytes for the pipe format in the following example).

Go read about .jsonl, json line. It's quite useful and I think it's what you're looking for. It's like CSV, where there's one record per line, but each line is a separate JSON. So you can append to that file. I used that a couple years ago. And I was able to analyze with power BI/excel get&transform. Some other software already works with it. Other json format extensions I've heard of is json5 and jsonc, which you probably might happened to interact with if you already used vscode and their settings.

Now with support for multiple batch tables in one input, I don't see a strong need for JSON implementation in the module. I still think multiple formats should be supported more generally outside individual modules. The new option at least supports a subset¹ of a well-documented version of CSV and Python users should be able to use the csv module.

Footnotes

1. Not supporting multiline columns because of its unpredictable length, but might be useful for the add tool to embed ASCII input; I think one edit per line should be better? ↩

[HuidaeCho]

I was wrong. Level 2 vector always requires topology building to remain level 2 even if there are no changes. Just tried this:

Vect_open_update2();
/* do nothing */
Vect_close();

Level 2 vector became level 1. I'm not sure why and how...

Please try #3459. If this works for you, you are welcome to include this single line in your PR and I close mine without merging.

Thanks for the PR. With that change, Vect_close() did the job, but G_fatal_error() still downgrades the level to 1 without an error handler (minor annoyance ;-).

[metzm]

Thanks for the PR. With that change, Vect_close() did the job, but G_fatal_error() still downgrades the level to 1 without an error handler (minor annoyance ;-).

Should be fixed with the latest commit to #3459. In case of a crash, the original topo info is (should be) preserved.

[wenzeslaus]

Can you please add a test? Both grass.gunittest and pytest would work here. pytest is now little easier than before because grass.script.create_location() does not require an existing session. grass.gunittest would be needed if you want to turn your example into a test. Python doc is quite good for CSV writing, but here is an example of CSV writer from a Python dictionary I recently wrote.

[HuidaeCho]

Can you please add a test? Both grass.gunittest and pytest would work here. pytest is now little easier than before because grass.script.create_location() does not require an existing session. grass.gunittest would be needed if you want to turn your example into a test. Python doc is quite good for CSV writing, but here is an example of CSV writer from a Python dictionary I recently wrote.

I'll do that when I get a chance.

[landam]

head -n2 /tmp/batch 
tool,cats,coords
break,1,"637108.11963224,257241.783755701"

v.edit map=roadsmajor_upper_half batch=/tmp/batch 
ERROR: Unknown batch column 'tool,cats,coords' in line 1

v.edit map=roadsmajor_upper_half batch=/tmp/batch sep=,
ERROR: Unable to open vector map <roadsmajor_upper_half> on topological
       level. Try to rebuild vector topology by v.build.

Please try it again.

Tested successfully.

[landam]

From my point of view, this PR may be merged when a new test for a batch option will be also added (and required CI tests will pass)