Generate Sqlite create table comments

[skalpin]

This only works with create table. Alter table commands do not preserve
comments.

Fixes #16820

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    Fixes #bugnumber

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[bricelam]

Also, do we want to handle table-level comments? Unfortunately, sqlite_master won't preserve comments before the CREATE TABLE statement, so we'd have to put them inside the table definition (which I don't like):

CREATE TABLE "Person" (
    -- Represents a person

    -- The ID
    "Id" INTEGER NOT NULL
)

[bricelam]

Hmm... another alternative I don't like:

CREATE TABLE "Person" ( -- Represents a person
    "Id" INTEGER NOT NULL, -- The ID
    "UndocumentedColumn1" TEXT,
    "UndocumentedColumn2" TEXT,
    "Name" TEXT -- The name
)

[bricelam]

My vote: Option B; omit spaces when no columns are documented; don't preserve table-level comments.

[skalpin]

I think I like this the best. If there is a table comment, there should be a line after. Then each column with a comment should have a newline before the comment.

CREATE TABLE "People" (
    -- Table Comment

    -- The ID
    "Id" INTEGER NOT NULL,
    "UndocumentedColumn1" TEXT,
    "UndocumentedColumn2" TEXT,

    -- The name
    "Name" TEXT
)

Do you like having a newline after the commented column better? like:

CREATE TABLE "People" (
    -- Table Comment

    -- The ID
    "Id" INTEGER NOT NULL,

    "UndocumentedColumn1" TEXT,
    "UndocumentedColumn2" TEXT,

    -- The name
    "Name" TEXT
)

[bricelam]

Do you like having a newline after the commented column better?

It's how I would write it, but just putting a newline before the comment is a simpler implementation, so I'd be fine with that too.

[bricelam]

LGTM. I'll let you decide what format we should use. ¯\(ツ)/¯ Do you think we should output table-level comments? Let me know when you're ready for me to merge it.

[bricelam]

We’ve taken a bug fix for code that did this somewhere else. I think it was about Unix line endings on Windows or something. I’ll try to find that implementation so we can reuse it here.

[ajcvickers]

@bricelam Remember to rebase on or cherry-pick to preview 9.

[bricelam]

@ajcvickers @smitpatel I'm breaking this (moving it to the general SQL generator so it can be shared with Migrations)