Potlatch 1/Remote calls/putway SQL

One of the most complex parts of the code within amf_controller.rb is the set of SQL statements (and supporting code) to write a way to the database ('putway'). 'deleteway', to delete a way, works similarly.

Here is how it works. 'Stage' numbers refer to comments in the code.

Contents 1 Stage 3: read original way into memory 2 Stage 4: get version 3 Stage 5: compare new nodes against old 4 Stage 6a: delete any nodes not in modified way 5 Stage 6b: insert new version of route into way_nodes 6 Stage 7: insert new way tags 7 Finally

Stage 3: read original way into memory

• If it's an existing way (i.e. way id>0):
  • Read the way's segments and nodes from the database (using the same query as 'getway')
  • Record the start/end nodes for each segment in a hash
  • Record x, y, tags for each node in further hashes
  • If we're writing a reverted/undeleted way, also record visible for each node
• If it's a new way (way id<0)
  • Create a new way in the database:
    • Insert new row into meta_ways
    • Insert new row into current_ways
  • Get its ID

Stage 4: get version

• Get version number by inserting new row into ways

Stage 5: compare new nodes against old

For each point in the array of points:

• Update bounding box
• If it's a new node (i.e. id<0) and not already created:
  • Create a new node in the db with these x/y/tags:
    • Insert new row into nodes
    • Insert new row into current_nodes
    • Record new id in renumberednodes so we can send it back to client
• Else if it already existed in this way:
  • Update if x, y or tags have changed:
    • Insert new row into nodes
    • Update current_nodes
• Otherwise ignore

Stage 6a: delete any nodes not in modified way

• Create temporary table containing all nodes that are:
  • in the previous version of this way
  • not in the new version of this way
  • not in any other way
• Delete each node in this table that isn't in the current way:
  • Insert new rows into nodes
  • Update current_nodes
  • Remove from any relations
• Drop temporary table

Stage 6b: insert new version of route into way_nodes

• Delete old version from current_way_nodes
• Insert rows into way_nodes
• Insert rows into current_way_nodes

Stage 7: insert new way tags

• Delete old version from current_way_tags
• Insert rows into way_tags
• Insert rows into current_way_tags

Finally

• Return 0 (success), original way ID, new way ID, hash of renumbered nodes, bounding box