Write hash

Purpose: Store key/value pair into a hash.

write-hash <hash> \
    key <key> \
    value <value> \
    [ status <status> ] \
    [ old-value <old value> ]

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write-hash will store string <key> (in "key" clause) and <value> (in "value" clause) into <hash>, which must be created with new-hash.

<key> and <value> are collectively called an "element".

If <key> already exists in the hash, then the old value associated with it is returned in string <old value> (in "old-value" clause) and <value> will replace the old value - in this case <status> number (in "status" clause) has a value of GG_INFO_EXIST.

If <key> did not exist, <status> will be GG_OKAY and <old value> is unchanged.

If a <hash> was created with "process-scope" clause (see new-hash), then the element (including <key> and <value>) will not be freed when the current request ends, rather it will persist while the process runs, unless deleted (see read-hash with delete clause).

Examples

Writing data to a hash:

new-hash h
write-hash h key "mykey" value "some data"

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Writing new value with the same key and obtaining the previous value (which is "some data"):

write-hash h key "mykey" value "new data" status st old-value od
if-true st equal GG_INFO_EXIST
    @Previous value for this key is <<print-out od>>
end-if

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The following is a key/value service, where a process-scoped hash is created. It provides inserting, deleting and querying key/value pairs. Such a service process can run indefinitely. Create file keysrv.golf:

%% /keysrv public
    do-once
    new-hash h hash-size 1024 process-scope
    end-do-once

    // Get input parameters
    get-param op
    get-param key
    get-param data

    if-true op equal "add" // Add data to hash 
        write-hash h key key value data old-value old_data status st
        if-true st equal GG_INFO_EXIST
            delete-string old_data
        end-if
        @Added [<<print-out key>>]
    else-if op equal "delete" // Delete data and obtain the value deleted
        read-hash h key (key) value val delete status st
        if-true st equal GG_ERR_EXIST
            @Not found [<<print-out key>>]
        else-if
            // If found, then delete key and value
            @Deleted [<<print-out val>>]
            delete-string val
        end-if
    else-if op equal "query" // Query hash based on key value
        read-hash h key (key) value val status st
        if-true st equal GG_ERR_EXIST
            @Not found, queried [<<print-out key>>]
        else-if
            @Value [<<print-out val>>]
        end-if
    end-if
%%

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Create and make the application, then run it as service:

// Create application
gg -k hash
// Make application
gg -q
// Start application (single process key service)
mgrg -w 1 hash

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Try it from a command line client (see gg):

// Add data
gg -r --req="/keysrv/op=add/key=15/data=15" --service --app="/hash" --exec
// Query data
gg -r --req="/keysrv/op=query/key=15" --service --app="/hash" --exec
// Delete data
gg -r --req="/keysrv/op=delete/key=15" --service --app="/hash" --exec

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See read-hash for more examples.