WIP: Implementation of window functions.

src/SQLite.jl

@@ -88,9 +88,12 @@ type SQLiteStmt{T}
     sql::T
 end
 
-sqliteprepare(db,sql,stmt,null) = 
+include("window.jl")
+export window
+
+sqliteprepare(db,sql,stmt,null) =
     @CHECK db sqlite3_prepare_v2(db.handle,utf8(sql),stmt,null)
-sqliteprepare(db::SQLiteDB{UTF16String},sql,stmt,null) = 
+sqliteprepare(db::SQLiteDB{UTF16String},sql,stmt,null) =
     @CHECK db sqlite3_prepare16_v2(db.handle,utf16(sql),stmt,null)
 
 function SQLiteStmt{T}(db::SQLiteDB{T},sql::AbstractString)
@@ -180,7 +183,7 @@ const SERIALIZATION = UInt8[0x11,0x01,0x02,0x0d,0x53,0x65,0x72,0x69,0x61,0x6c,0x
 function sqldeserialize(r)
     ret = ccall(:memcmp, Int32, (Ptr{UInt8},Ptr{UInt8}, UInt),
             SERIALIZATION, r, min(18,length(r)))
-    
+
     if ret == 0
         v = deserialize(IOBuffer(r))
         return v.object
@@ -205,7 +208,7 @@ function query(db::SQLiteDB,sql::AbstractString, values=[])
     end
     while status == SQLITE_ROW
         for i = 1:ncols
-            t = sqlite3_column_type(stmt.handle,i-1) 
+            t = sqlite3_column_type(stmt.handle,i-1)
             if t == SQLITE_INTEGER
                 r = sqlite3_column_int64(stmt.handle,i-1)
             elseif t == SQLITE_FLOAT

src/window.jl

@@ -0,0 +1,62 @@
+addrange(i::Integer, r::UnitRange) = (i + r.start):(i + r.stop)
+addrange(i::Integer, r::StepRange) = (i + r.start):r.step:(i + r.stop)
+
+function fetchrow(stmt::SQLiteStmt, ncols::Integer)
+    row = Any[]
+    for col in 1:ncols
+        t = sqlite3_column_type(stmt.handle,col-1)
+        if t == SQLITE_INTEGER
+            r = sqlite3_column_int64(stmt.handle,col-1)
+        elseif t == SQLITE_FLOAT
+            r = sqlite3_column_double(stmt.handle,col-1)
+        elseif t == SQLITE_TEXT
+            #TODO: have a way to return text16?
+            r = bytestring(sqlite3_column_text(stmt.handle,col-1))
+        elseif t == SQLITE_BLOB
+            blob = sqlite3_column_blob(stmt.handle,col-1)
+            b = sqlite3_column_bytes(stmt.handle,col-1)
+            buf = zeros(UInt8,b)
+            unsafe_copy!(pointer(buf), convert(Ptr{UInt8},blob), b)
+            r = sqldeserialize(buf)
+        else
+            r = NULL
+        end
+        push!(row, r)
+    end
+    status = sqlite3_step(stmt.handle)
+    status, row
+end
+
+function window{S<:AbstractString}(
+    db::SQLiteDB, cb::Base.Callable, range::OrdinalRange,
+    table::AbstractString, columns::Vector{S}, data=nothing,
+)
+    @assert !isempty(columns) "you must specifiy at least one column"
+    nrows = query(db, string("SELECT COUNT(*) FROM ", table))[1][1]
+    stmt = SQLiteStmt(db, string("SELECT ", join(columns, ", "), " FROM ", table))
+    status = execute(stmt)
+    ncols = sqlite3_column_count(stmt.handle)
+    # TODO: we can calculate how many rows we need and do this in place
+    tablerows = Array{Any,1}[]
+    results = Any[]
+    latest_row = 0
+    for start_row in 1:(nrows + range.start - range.stop)
+        # TODO: we can do this in place aswell
+        curwindow = Array{Any,1}[]
+        # find relevent rows for window
+        for row in range
+            # only load rows as they are needed
+            while latest_row < row + start_row - 1 && status == SQLITE_ROW
+                status, row_values = fetchrow(stmt, ncols)
+                latest_row += 1
+                push!(tablerows, row_values)
+            end
+            status == SQLITE_ROW || status == SQLITE_DONE || sqliteerror(stmt.db)
+            push!(curwindow, tablerows[row])
+        end
+        push!(results, cb(curwindow, range, data))
+        # get rid of rows we no longer need
+        shift!(tablerows)
+    end
+    results
+end