path: root/lib/dblib.lua

--[[

/*
 *  Baltisot
 *  Copyright (C) 1999-2008 Nicolas "Pixel" Noble
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

]]--

-- dblib - database object layer
-- Currently built-in with MySQL and Oracle support. MySQL is the default one.

--[[

ddl = {
    field1 = { type = "varchar", length = 32 },
    field2 = { type = "number", length = 11, decimal = 8, default = 42 },
    id = { options = "pri,auto" },
}

db = luadb.mysql.opendb(host, login, password, database)
t = db:opentable("foobar", ddl)
t:empty()

x = t:insert{ field1 = "test1" }              -- returns 1
x = t:insert{ field1 = "test2" }              -- returns 2
x = t:insert{ field1 = "test3" }              -- returns 3
x = t:insert{ field1 = "test4", field2 = 18 } -- returns 4
x = t:insert{ field1 = "test5", field2 = 20 } -- returns 5

r = t:restricter()

t:restrict(r:EQ("id", 3))             -- WHERE `id` = "3"
x = t:update{ field1 = "3tset" }      -- returns 1
t:restrict(r:EQ("field2", 42))        -- WHERE `field2` = "42"
x = t:update{ field2 = 28 }           -- returns 3
t:restrict(r:EQ("id", 4))             -- WHERE `id` = "4"
x = t:delete()                        -- returns 1
t:restrict(r:AND(r:LIKE("field1", "test%"), r:NEQ("field2", 20)))
                                      -- WHERE `field` LIKE "test%" AND `field2` != 20
for r in t:gselect{ "field1" } do print(r.field1) end
                                      -- prints the strings "test1" and "test2"
t:restrict(r:LIKE("field1", "test%"))
print(t:count())                      -- prints "3"
t:restrict()                          -- WHERE 1
t:select()
print(t:numrows())                    -- prints "4"
print(t:numfields())                  -- prints "3"
row = t:nextrow()
print(row.field1)                     -- prints "test1"

]]--

_luadb = {
    get_options = function(str)
        local s = split(str, ",")
        local r = {}
        for k, v in pairs(s) do
            r[v:upper()] = true
        end
        
        return r
    end,
    
    get_canon_type = function(ttype, k, db)
        if ttype == nil then
            return "INT"
        elseif type(ttype) ~= "string" then
            error("Wrong data in ddl - " .. k .. ".type isn't a string.")
        elseif ttype:upper() == "VARCHAR" then
            return "VARCHAR"
        elseif ttype:upper() == "INT" then
            return "INT"
        elseif ttype:upper() == "BLOB" then
            return "BLOB"
        elseif ttype:upper() == "TIMESTAMP" then
            return "TIMESTAMP"
        elseif ttype:upper() == "NUMBER" then
            if db._.odbc_name == "mysql" then
                return "FLOAT"
            end
            return "NUMBER"
        elseif ttype:upper() == "FLOAT" then
            return "NUMBER"
        elseif ttype:upper() == "TEXT" then
            return "TEXT"
        else
            error("Unknow data type in ddl - " .. k .. ": " .. ttype:upper())
        end            
    end,

    generate_fields = function(db, tablename, ddl)
        local k, v
        local r, alters, keys, extras = {}, {}, {}, {}
        
        for k, v in pairs(ddl) do
            local ttype
            r[k] = ""
            alters[k] = {}
            
            ttype = _luadb.get_canon_type(v.type, k, db)
            if ttype == "TEXT" and db._.odbc_name == "oracle" then ttype = "CLOB" end
            r[k] = ttype
            
            if v.length == nil then
                -- do nothing
            elseif type(v.length) ~= "number" then
                error("Wrong data in ddl - " .. k .. ".length isn't a number.")
            elseif v.decimal == nil then
                r[k] = r[k] .. "(" .. v.length .. ")"
            elseif type(v.decimal) ~= "number" then
                error("Wrong data in ddl - " .. k .. ".decimal isn't a number.")
            else
                r[k] = r[k] .. "(" .. v.length .. "," .. v.decimal .. ")"
            end
            
            if v.options ~= nil and type(v.options) ~= "string" then
                error("Wrong data in ddl for table " .. tablename .. " - " .. k .. ".options isn't a string.")
            end
            
            local options = v.options and _luadb.get_options(v.options) or {}
            
            if options.PRI then
                table.insert(keys, k)
                keys[k] = true
            end
            
            if options.UNIQ then
                table.insert(alters[k], "ADD UNIQUE (" .. db._.fq .. "@fieldname@" .. db._.fq .. ")")
            end

            if options.AUTO then
                if db._.odbc_name == "mysql" then
                    r[k] = r[k] .. " AUTO_INCREMENT"
                elseif db._.odbc_name == "oracle" then
                    local seq = "seq_" .. db.sql_escape(tablename .. "_" .. k)
                    local trg = "trg_" .. db.sql_escape(tablename .. "_" .. k) .. "_auto"
                    local owner = db._.prefix == "" and "USER()" or ("'" .. db._.prefix .. "'")
                    local tbl = db.sql_escape(tablename)
                    local fld = db.sql_escape(k)
                    table.insert(extras, [[
DECLARE
    P_EXISTS NUMBER;
BEGIN
    SELECT COUNT(*) INTO P_EXISTS FROM ALL_SEQUENCES WHERE SEQUENCE_NAME=']] .. seq .. [[' AND SEQUENCE_OWNER=]] .. owner .. [[;
    IF P_EXISTS = 0 THEN
        EXECUTE IMMEDIATE 'CREATE SEQUENCE "]] .. seq .. [["';
    END IF;
END;
]])
                    table.insert(extras, [[
CREATE OR REPLACE TRIGGER "]] .. trg .. [["
    BEFORE INSERT ON "]] .. tbl .. [["
    FOR EACH ROW BEGIN IF :new."]] .. fld .. [[" IS NULL THEN
        SELECT "]] .. seq .. [[".nextval INTO :new."]] .. fld .. [[" FROM DUAL;
    END IF;
END;
]])
                else
                    error("Unknown odbc for auto increment operations.")
                end
            end
            
            if v.default then
                if type(v.default) ~= "string" and type(v.default) ~= "number" then
                    error("Default value for field " .. k .. " isn't usable.")
                end
                r[k] = r[k] .. ' DEFAULT ' .. db._.eq .. db.sql_escape(v.default) .. db._.eq
            elseif ttype == "TIMESTAMP" then
                r[k] = r[k] .. ' DEFAULT CURRENT_TIMESTAMP'
            end

            if options.NULL then
                r[k] = r[k] .. " NULL"
            else
                r[k] = r[k] .. " NOT NULL"
            end
            
        end
        return r, alters, keys, extras
    end,
    
    newtable = function(tablename, tname, db, ddl)
        return {
            insert = _luadb.insert,
            delete = _luadb.delete,
            select = _luadb.select,
            gselect = _luadb.gselect,
            rselect = _luadb.rselect,
            grselect = _luadb.grselect,
            update = _luadb.update,
            pinsert = function(...) return pcall(_luadb.insert, ...) end,
            pdelete = function(...) return pcall(_luadb.delete, ...) end,
            pselect = function(...) return pcall(_luadb.select, ...) end,
            pgselect = function(...) return pcall(_luadb.gselect, ...) end,
            prselect = function(...) return pcall(_luadb.rselect, ...) end,
            pgrselect = function(...) return pcall(_luadb.grselect, ...) end,
            pupdate = function(...) return pcall(_luadb.update, ...) end,
            numrows = _luadb.numrows,
            numfields = _luadb.numfields,
            nextrow = _luadb.nextrow,
            count = _luadb.count,
            restrict = _luadb.restrict,
            restricter = _luadb.restricter,
            empty = _luadb.empty,
            _ = {
                tablename = tablename,
                tname = tname,
                db = db,
                ddl = ddl,
                conditions = "1=1",
            },
        }
    end,
    
    opentable = function(db, tablename, ddl, force_create)
        local tname
        if db._.prefix and db._.prefix ~= "" and db._.odbc_name == "oracle" then
            tname = db._.fq .. db._.prefix .. db._.fq .. '.' .. db._.fq .. db.sql_escape(tablename) .. db._.fq
        else
            tname = db._.fq .. db._.prefix .. db.sql_escape(tablename) .. db._.fq
        end
        if not ddl then return _luadb.newtable(tablename, tname, db, ddl) end
        local fields, alters, keys, extras = _luadb.generate_fields(db, tablename, ddl)
        local operations = 0
        local dfields = db:Desc(tablename)
        
        if force_create or dfields == nil then
            -- table doesn't exist, create it
            local q = "CREATE TABLE " .. tname .. " ("
            local k, v, first
            first = true
            operations = -1
            
            for k, v in pairs(fields) do
                if not first then
                    q = q .. ", "
                else
                    first = false
                end
                q = q .. db._.fq .. db.sql_escape(k) .. db._.fq .. " " .. v
            end
            
            if #keys ~= 0 then
                q = q .. ", PRIMARY KEY ("
                first = true
                for k, v in ipairs(keys) do
                    if not first then
                        q = q .. ", "
                    else
                        first = false
                    end
                    q = q .. db._.fq .. db.sql_escape(v) .. db._.fq
                end
                q = q .. ")"
            end
            
            q = q .. ")"
            
            if db._.odbc_name == "mysql" then
                q = q .. " ENGINE=InnoDB"
            end
            
            q = q .. ";"
            
            if db:SafeQuery(q, "update") ~= 0 then
                error("Error creating table " .. tname .. ": " .. db:ErrorStr() .. " - query run = " .. q)
            end
            
            for k, v in pairs(alters) do
                local _, stmt
                for _, stmt in pairs(v) do
                    q = "ALTER TABLE " .. tname .. " " .. string.gsub(stmt, "@fieldname@", db.sql_escape(k))
                    if db:SafeQuery(q, "update") ~= 0 then
                        error("Error altering table " .. tname .. ": " .. db:ErrorStr() .. " - query run = " .. q)
                        db:SafeQuery("DROP TABLE " .. tname .. ";", "update")
                    end
                end
            end

            for k, v in pairs(extras) do
                if db:SafeQuery(v, "raw") ~= 0 then
                    error("Error running extra query for " .. tname .. ": " .. db:ErrorStr() .. " - query run = " .. v)
                    db:SafeQuery("DROP TABLE " .. tname .. ";", "update")
                end
            end
        else
            -- table exists, let's check it.
            local i
            local any_common = false
            
            for i = 1, #dfields do
                if fields[dfields[i].Field] then
                    any_common = true
                end
            end
            
            if not any_common then
                -- strictly no field in common; drop the table and tail-call opentable in order to proceed with a createtable instead.
                q = "DROP TABLE " .. tname .. ";"
                if db:SafeQuery(q, "update") ~= 0 then
                    error("Error dropping table " .. tname .. ": " .. db:ErrorStr() .. " - query run = " .. q)
                end
                return db:opentable(tablename, ddl, true)
            end
            
            local d, k, v = {}
            
            for k, v in pairs(dfields) do
                d[v.Field] = v
                if not fields[v.Field] then
                    q = "ALTER TABLE " .. tname .. " DROP COLUMN " .. db._.fq .. db.sql_escape(v.Field) .. db._.fq .. ";"
                    if db:SafeQuery(q, "update") ~= 0 then
                        error("Error altering table " .. tname .. ": " .. db:ErrorStr() .. " - query run = " .. q)
                    end
                    operations = operations + 1
                end
            end
            dfields, d = d, nil
            
            local deffered_alters = {}
            
            for k, v in pairs(fields) do
                q = nil
                if not dfields[k] then
                    q = "ALTER TABLE " .. tname .. " ADD " .. db._.fq .. db.sql_escape(k) .. db._.fq .. " " .. v .. ";"
                else
                    local identicals, alters = _luadb.compare_fields(db, ddl, dfields[k])
                    if not identicals then
                        q = "ALTER TABLE " .. tname .. " MODIFY " .. db._.fq .. db.sql_escape(k) .. db._.fq .. " " .. v .. ";"
                        local _, a
                        for _, a in pairs(alters) do
                            a.stmt = string.gsub(a.stmt, "@fieldname@", db.sql_escape(k))
                            if a.pri < 0 then
                                table.insert(deffered_alters, a)
                            else
                                q = "ALTER TABLE " .. tname .. " " .. a.stmt .. ";"
                                if db:SafeQuery(q, "update") ~= 0 then
                                    error("Error altering table " .. tname .. ": " .. db:ErrorStr() .. " - query run = " .. q)
                                end
                                operations = operations + 1
                            end
                        end
                    end
                end
                if q then
                    if db:SafeQuery(q, "update") ~= 0 then
                        error("Error altering table " .. tname .. ": " .. db:ErrorStr() .. " - query run = " .. q)
                    end
                    operations = operations + 1
                end
            end
            
            table.sort(deffered_alters, function(a, b) return a.pri < b.pri end)
            
            for k, v in pairs(deffered_alters) do
                q = "ALTER TABLE " .. tname .. " " .. v.stmt .. ";"
                if db:SafeQuery(q, "update") ~= 0 then
                    error("Error altering table " .. tname .. ": " .. db:ErrorStr() .. " - query run = " .. q)
                end
                operations = operations + 1
            end
        end
        
        return newtable(tablename, tname, db, ddl), operations
    end,

    compare_fields = function(db, ddl, field)
        local f = field.Field
        local identical = true
        local alters = {}
        if type(ddl[f]) ~= "table" then
            error("Internal issue with the DDL: key " .. f .. " isn't a table.")
        end
        -- check base type first.
        local ddltype = _luadb.get_canon_type(ddl[f].type, f, db)
        local desctype, desclength, descdecim = field.Type:match "(%w+)%((%d+)%,(%d+)%)"
        if desctype == nil then
            desctype, desclength = field.Type:match "(%w+)%((%d+)%)"
        end
        if desctype == nil then
            desctype = field.Type:match "(%w+)"
        end
        if desctype == nil then
            error("Error parsing type string from database: " .. f .. ": " .. field.Type)
        end
        desctype = _luadb.get_canon_type(desctype, f, db)
        
        if ddltype ~= desctype then
            identical = false
        end
        
        if field.length and field.length ~= desclength then
            identical = false
        end
        
        if field.decimal and field.decimal ~= descdecim then
            identical = false
        end

        local options = ddl[f].options and _luadb.get_options(ddl[f].options) or {}
        
        if options.PRI and field.Key ~= "PRI" then
            -- needs to add a primary key here, with a specific ALTER TABLE statement
            identical = false
            table.insert(alters, { stmt = "ADD PRIMARY KEY(@fieldname@)", pri = -1 } )
        end
        
        if not options.PRI and field.Key == "PRI" then
            -- needs to drop the primary key here.
            identical = false
            table.insert(alters, { stmt = "DROP PRIMARY KEY", pri = -2 } )
        end
        
        -- Needs oracle version of this...
        if db._.odbc_name == "mysql" then
            if options.UNI and field.Key ~= "UNI" then
                -- needs to add a unique index
                identical = false
                table.insert(alters, { stmt = "ADD UNIQUE(@fieldname@)", pri = 0 } )
            end
        
            if not options.UNI and field.Key == "UNI" then
                -- needs to drop the unique index
                identical = false
                table.insert(alters, { stmt = "DROP INDEX @fieldname@", pri = 0 } )
            end
        end
        
        -- Need oracle version of this check.
        if db._.odbc_name == "mysql" then
            if not options.AUTO and field.Extra == "auto_increment" then
                identical = false
            end
        end
        
        if db._.odbc_name == "mysql" then
            if options.AUTO and field.Extra ~= "auto_increment" then
                identical = false
            end
        end
        
        return identical, alters
    end,
    
    insert = function(t, data)
        local k, v, stmt, stmt2
        local first = true
        local got_blobs = false
        
        stmt = "INSERT INTO " .. t._.tname .. " ("
        stmt2 = ") VALUES ("
        
        for k, v in pairs(data) do
            if not t._.ddl[k] then
                error("Trying to address a field which doesn't exist: " .. k .. " - inside of table " .. t._.tablename)
            end
            local ftype = _luadb.get_canon_type(t._.ddl[k].type, k, t._.db)
            if t._.db._.odbc_name == "oracle" and (ftype == "BLOB" or ftype == "TEXT") then
                got_blobs = true
            else
                if not first then
                    stmt = stmt .. ", "
                    stmt2 = stmt2 .. ", "
                else
                    first = false
                end
                stmt = stmt .. t._.db._.fq .. k .. t._.db._.fq
                stmt2 = stmt2 .. t._.db._.eq .. v .. t._.db._.eq
            end
        end

        if t._.db._.odbc_name == "oracle" then
            local conn, stmt, status = t._.db._.conn
            stmt = conn:createStatement(stmt .. stmt2 .. ") RETURNING ROWIDTOCHAR(rowid) INTO :1")
            stmt:registerOutParam(1, OCCISTRING, 30, "VARCHAR2")
            status = stmt:executeUpdate()
            if status ~= 1 then
                error("Error inserting a row inside table " .. t._.tablename .. ": " .. stmt:getErrorMsg())
            end
            t._.db._.lastId = stmt:getString(1)
            conn:terminateStatement(stmt)
        else
            if t._.db:SafeQuery(stmt .. stmt2 .. ");", "update") ~= 0 then
                error("Error inserting a row inside table " .. t._.tablename .. ": " .. t._.db:Error())
            end
        end
        
        if t._.db._.odbc_name == "mysql" then
            t._.db._.lastId = t._.db._.conn:InsertId()
        end
        
        return t._.db._.lastId
    end,
    
    delete = function(t)
        local stmt = "DELETE FROM " .. t._.tname .. " WHERE " .. t._.conditions .. ";"
        
        if t._.db:SafeQuery(stmt, "update") ~= 0 then
            error("Error deleting row(s) inside table " .. t._.tablename .. ": " .. t._.db:Error())
        end
        if t._.db._.odbc_name == "mysql" then
            t._.db._.lastAffectedRows = t._.db._.conn:NumAffectedRows()
        elseif t._.db._.odbc_name == "oracle" then
            t._.db._.lastAffectedRows = t._.db._.affectedRows
        else
            error("Don't know how to handle odbc " .. t._.db._.odbc_name .. " in update.")
        end
        
        return t._.db._.lastAffectedRows
    end,
    
    update = function(t, data)
        local stmt = "UPDATE " .. t._.tname .. " SET "
        local first = true
        local got_blobs = false
        local k, v
        
        for k, v in pairs(data) do
            if not t._.ddl[k] then
                error("Trying to update a field which doesn't exist: " .. k .. " - inside of table " .. t._.tablename)
            end
            local ftype = _luadb.get_canon_type(t._.ddl[k].type, k, t._.db)
            if t._.db._.odbc_name == "oracle" and (ftype == "BLOB" or ftype == "TEXT") then
                got_blobs = true
            else
                if not first then
                    stmt = stmt .. ", "
                else
                    first = false
                end
                stmt = stmt .. t._.db._.fq .. t._.db.sql_escape(k) .. t._.db._.fq .. "="
                if type(v) == "string" or type(v) == "number" then
                    stmt = stmt .. t._.db._.eq .. t._.db.sql_escape(v) .. t._.db._.eq
                else
                    error("Complex UPDATE queries are not supported yet.")
                end
            end
        end
        
        stmt = stmt .. " WHERE " .. t._.conditions
        
        if t._.db:SafeQuery(stmt, "update", got_blobs) ~= 0 then
            error("Error updating row(s) inside table " .. t._.tablename .. ": " .. t._.db:Error())
        end
        if t._.db._.odbc_name == "mysql" then
            t._.db._.lastAffectedRows = t._.db._.conn:NumAffectedRows()
        elseif t._.db._.odbc_name == "oracle" then
            t._.db._.lastAffectedRows = t._.db._.affectedRows
        else
            error("Don't know how to handle odbc " .. t._.db._.odbc_name .. " in update.")
        end
        
        if got_blobs then
            -- very ugly way to solve this, but... *shrug*
            local conn, buffs, count, stmt, rset = t._.db._.conn, {}, 1
            stmt = "SELECT "
            first = false
            for k, v in pairs(data) do
                local ftype = _luadb.get_canon_type(t._.ddl[k].type, k, t._.db)
                if ftype == "BLOB" or ftype == "TEXT" then
                    if not first then
                        stmt = stmt .. ", "
                    else
                        first = false
                    end
                    stmt = stmt .. t._.db._.fq .. t._.db.sql_escape(k) .. t._.db._.fq
                end
                buffs[count] = Buffer(true)
                buffs[count]:write(v)
                count = count + 1
            end
            stmt = stmt .. " FROM " .. t._.tname .. " WHERE " .. t._.conditions .. " FOR UPDATE"
            stmt = conn:createStatement(stmt)
            rset = stmt:executeQuery()
            while rset:next() ~= 0 do
                for k, v in ipairs(buffs) do
                    rset:setBlob(k, v)
                    v:seek(0, SEEK_SET)
                end
            end
            for k, v in ipairs(buffs) do
                v:destroy()
            end
            conn:commit()
            stmt:closeResultSet(rset)
            conn:terminateStatement(stmt)
        end
        
        return t._.db._.lastAffectedRows
    end,
    
    iselect = function(bypass, t, fields, foreign, options)
        local stmt = "SELECT "
        local first = true
        local k, v

        if fields == nil then
            stmt = stmt .. "*"
        else        
            for k, v in pairs(fields) do
                local is_foreign = false
                if foreign then
                    local _, f
                    for _, f in pairs(foreign) do
                        if f._.ddl[v] then
                            is_foreign = true
                        end
                    end
                end
                if not bypass and not is_foreign and not t._.ddl[v] then
                    error("Trying to select a field which doesn't exist: " .. k .. " - inside of table " .. t._.tablename)
                end
                if not first then
                    stmt = stmt .. ", "
                else
                    first = false
                end
                if bypass then
		    stmt = stmt .. v
                else
		    stmt = stmt .. t._.db._.fq .. v .. t._.db._.fq
		end
            end
        end
        
        if foreign then
            local foreign_conds = "1=1"
            stmt = stmt .. " FROM " .. t._.tname
            local found_table, fname, f
            for k, v in pairs(foreign) do
                stmt = stmt .. ", " .. v._.tname
                found_table = false
                for fname, f in pairs(t._.ddl) do
                    if f.foreign and f.foreign.tablename == v._.tablename then
                        if not v._.ddl[f.foreign.fieldname] then
                            error("Foreign key points to an unknown field in table: " .. f.foreign.tablename .. "." .. f.foreign.fieldname)
                        end
                        foreign_conds = foreign_conds .. " AND " .. t._.tname .. "." .. t._.db._.fq .. fname .. t._.db._.fq "=" .. v._.tname .. "." .. t._.db._.fq .. f.foreign.fieldname .. t._.db._.fq
                        found_table = true
                    end
                end
                if not found_table then
                    error("Foreign table " .. v._.tablename .. " specified in request didn't match any of the foreign key of table " .. t._.tablename)
                end
            end
            stmt = stmt .. " WHERE (" .. t._.conditions .. ") AND (" .. foreign_conds .. ")"
        else
            stmt = stmt .. " FROM " .. t._.tname .. " WHERE " .. t._.conditions
        end
        
        if options then
            if options.order then
                local direction = "ASC"
                if type(options.order) ~= "table" then
                    error("Wrong type for options.order; should be a table.")
                end
                if type(options.order.by) ~= "string" then
                    error("The order option has to contain one valid 'by' field.")
                end
                if options.order.dir then
                    if type(options.order.dir) ~= "string" then
                        error("options.order.dir has to be a string")
                    end
                    if options.order.dir:upper() == "ASC" then
                        direction = "ASC"
                    elseif options.order.dir:upper() == "DESC" then
                        direction = "DESC"
                    else
                        error("options.order.dir has to be either 'asc' or 'desc'")
                    end
                end
                stmt = stmt .. " ORDER BY " .. t._.db._.fq .. options.order.by .. t._.db._.fq .. " " .. direction
            end
            if options.limit then
                if type(options.limit) ~= "table" then
                    error("Wrong type for options.limit; should be a table.")
                end
                local start, size = 0, 30
                if options.limit.start then
                    if type(options.limit.start) ~= "number" then
                        error("options.limit.start has to be a number")
                    end
                    start = options.limit.start
                end
                if options.limit.size then
                    if type(options.limit.size) ~= "number" then
                        error("options.limit.size has to be a number")
                    end
                    size = options.limit.size
                end
                if t._.db._.odbc_name == "mysql" then
                    stmt = stmt .. " LIMIT " .. start .. "," .. size
                elseif t._.db._.odbc_name == "oracle" then
                    error("LIMIT code for Oracle not implemented yet.")
                else
                    error("No LIMIT code - unknown odbc")
                end
            end
        end
        
        stmt = stmt .. ";"
        
        if t._.db:SafeQuery(stmt, "query") ~= 0 then
            error("Error selecting row(s) inside table " .. t._.tablename .. ": " .. t._.db:ErrorStr())
        end
        
        return (t._.db._.odbc_name == "oracle" and -1 or t:numrows()), t:numfields()
    end,
    
    empty = function(t, fields)
        if t._.db:SafeQuery("TRUNCATE TABLE " .. t._.tname, "update") ~= 0 then
            error("Error emptying table " .. t._.tablename .. ": " .. t._.db:Error())
        end
    end,
    
    select = function(...)
        return _luadb.iselect(false, ...)
    end,
    
    rselect = function(...)
        return _luadb.iselect(true, ...)
    end,
    
    numrows = function(t)
        if t._.db._.odbc_name == "mysql" then
	    return t._.db._.conn:NumRows()
	elseif t._.db._.odbc_name == "oracle" then
	    error "No 'numrows' for Oracle yet."
	else
	    error "Unknown odbc for numrows."
	end
    end,
    
    numfields = function(t)
        if t._.db._.odbc_name == "mysql" then
	    return t._.db._.conn:NumFields()
	elseif t._.db._.odbc_name == "oracle" then
	    return t._.db._.numFields
	else
	    error "Unknown odbc for numfields."
	end
    end,
    
    count = function(t)
	_luadb.iselect(true, t, {"COUNT(*) AS count"})
	local row = t:nextrow()
	return row.count or row.COUNT
    end,
    
    gselect = function(t, ...)
	_luadb.iselect(false, t, ...)
        return t.nextrow, t
    end,
    
    grselect = function(t, ...)
	_luadb.iselect(true, t, ...)
        return t.nextrow, t
    end,
    
    nextrow = function(t)
        if t._.db._.odbc_name == "mysql" then
            return t._.db._.conn:FetchRow()
        elseif t._.db._.odbc_name == "oracle" then
            local row = nil
            if t._.db._.rset:next() ~= 0 then
                row = {}
                for k, v in pairs(t._.db._.fieldsNames) do
                    row[v] = t._.db._.rset:getString(k)
                end
            end
            return row
        else
            error "Unknown odbc for nextrow."
        end
    end,
    
    _restricts = {
        -- All the rendering is done on-the-fly.
        -- this is the leaf function; thus this is the only one which ough to get the sql_escape.
        dop = function(r, field, expr, op)
            if not r._.tbl._.ddl[field] then
                error("Trying to restrict on a field which doesn't exist: " .. field .. " - inside of table " .. r._.tbl._.tablename)
            end
            
            if type(expr) == "string" or type(expr) == "number" then
                return r._.tbl._.tname .. "." .. r._.tbl._.db._.fq .. field .. r._.tbl._.db._.fq .. " " .. op .. " " .. r._.tbl._.db._.eq .. r._.tbl._.db.sql_escape(expr) .. r._.tbl._.db._.eq
            elseif type(expr) == "table" then
                error("Complex queries not handled for now")
            else
                error("Wrong type for expression in operator: " .. type(expr))
            end
        end,
        
        varops = function(r, op, ...)
            local exprs, first, r, k, v = {...}, true, ""
            
            for k, v in pairs(exprs) do
                if not first then
                    r = r .. " " .. op .. " "
                end
                r = r .. v
                first = false
            end
            return r
        end,
    },
    
    restricts = {
        NOT = function(r, expr)
            return "NOT " .. expr
        end,
        
        AND = function(r, ...) return _luadb._restricts.varops(r, "AND", ...) end,
        OR = function(r, ...) return _luadb._restricts.varops(r, "OR", ...) end,
        
        EQ = function(r, field, expr) return _luadb._restricts.dop(r, field, expr, "=") end,
        NEQ = function(r, field, expr) return _luadb._restricts.dop(r, field, expr, "!=") end,
        GT = function(r, field, expr) return _luadb._restricts.dop(r, field, expr, ">") end,
        LT = function(r, field, expr) return _luadb._restricts.dop(r, field, expr, "<") end,
        GE = function(r, field, expr) return _luadb._restricts.dop(r, field, expr, ">=") end,
        LE = function(r, field, expr) return _luadb._restricts.dop(r, field, expr, "<=") end,
        LIKE = function(r, field, expr) return _luadb._restricts.dop(r, field, expr, "LIKE") end,
        IN = function(r, field, expr) return _luadb._restricts.dop(r, field, expr, "IN") end,
    },
    
    restricter = function(t)
        local r, k, v = { _ = { tbl = t } }
        
        for k, v in pairs(_luadb.restricts) do
            r[k] = v
        end
        
        return r
    end,
    
    restrict = function(t, conditions)
        -- all in all, "conditions" can just be a direct string. Let the programmer do what he wants, after all.
        if conditions == nil or conditions == "" then conditions = "1=1" end
        t._.conditions = conditions
    end,

    mysql = {
        SafeQuery = function(db, str, query_type, no_commit)
            if luadb.debugmode then
                print(str)
            end
        
            local r = db._.conn:Query(str)
            if r ~= 0 and db._.conn:ErrNO() == 2006 then -- disconnected
                db._.conn = luadb:opendb(db)._.conn
                r = db._.conn:Query(str)
            end
        
            return r
        end,
        
        Desc = function(db, tbl)            
            if db:SafeQuery("DESC " .. db._.fq .. db._.prefix .. db.sql_escape(tbl) .. db._.fq .. ";") ~= 0 then return nil end
            
            local dfields = {}
            for i = 1, db._.conn:NumRows() do
                dfields[i] = db._.conn:FetchRow()
            end
            
            return dfields
        end,
    },
    
    oracle = {
        _SafeQuery = function(db, str, query_type, no_commit)
            local r = -1
            
            if luadb.debugmode then
                print(str)
            end
        
            if not query_type then
                error "SafeQuery: Need a query type"
            end
            
            if db._.stmt then
                if db._.rset then
                    db._.stmt:closeResultSet(db._.rset)
                    db._.rset = nil
                end
                db._.conn:terminateStatement(db._.stmt)
            end
        
            local stmt = db._.conn:createStatement()
            
            if query_type == "update" or query_type == "raw" then
                if query_type == "update" then
                    str = str:gsub("%s*(.*)%s*;", "%1")
                end
                db._.affectedRows = stmt:executeUpdate(str)
                if db._.affectedRows == nil then
                    db._.errNO = stmt:getErrorCode()
                    db._.errStr = stmt:getErrorMsg()
                    db._.numFields = 0
                    db._.fieldsNames = {}
                    db._.rset = nil
                else
                    db._.errNO = 0
                    db._.errStr = "No error"
                    db._.numFields = 0
                    db._.fieldsNames = {}
                    db._.rset = nil
                    r = 0
                end
            elseif query_type == "query" then
                str = str:gsub("%s*(.*)%s*;", "%1")
                local rset = stmt:executeQuery(str)
                if rset then
                    db._.errNO = 0
                    db._.errStr = "No error"
                    db._.numFields, db._.fieldsNames = rset:getFieldsInfo()
                    db._.rset = rset
                    r = 0
                else
                    db._.errNO = stmt:getErrorCode()
                    db._.errStr = stmt:getErrorMsg()
                    db._.numFields = 0
                    db._.fieldsNames = {}
                    db._.rset = nil
                end
            elseif type(query_type) == "string" then
                error("Unknown query type: " .. query_type)
            else
                error("Query type mis-specified (not a string)")
            end
        
            db._.stmt = stmt
            
            if r == 0 and not no_commit then
                db._.conn:commit()
            end
        
            return r
        end,
        
        SafeQuery = function(db, str, query_type, no_commit)
            local r = _luadb.oracle._SafeQuery(db, str, query_type, no_commit)
            if r ~= 0 then
                -- connection timeout, let's reconnect.
                if db._.errNO == 3135 then
                    if db._.stmt then
                        if db._.rset then
                            db._.stmt:closeResultSet(db._.rset)
                            db._.rset = nil
                        end
                        db._.conn:terminateStatement(db._.stmt)
                    end
                    db._.conn = luadb.oracle.opendb(db)._.conn
                    r = _luadb.oracle._SafeQuery(db, str, query_type, no_commit)
                end
            end
            
            return r
        end,
        
        oracle_types = {
            [1] = "VARCHAR",
            [2] = "NUMBER",
            [12] = "DATE",
            [96] = "CHAR",
            [180] = "TIMESTAMP",
            [113] = "BLOB",
            [112] = "CLOB",
        },
        
        Desc = function(db, tbl)
            if db:SafeQuery("SELECT DBMS_METADATA.GET_XML('TABLE', '" .. db.sql_escape(tbl) .. "'" .. ((db._.prefix and db._.prefix ~= "") and (", '" .. db.sql_escape(db._.prefix) .. "'") or "") .. ") FROM USER_TABLES;", "query") ~= 0 then
                if db:ErrNO() == 31603 then
                    return nil
                end
                error("Couldn't properly read the description of table " .. tbl .. " - error: " .. db:ErrorStr())
            end
            local n = db._.rset:next()
            if n == 0 or not n then
                error("Error retrieving table description: no resultset available.")
            end
            local ddl = flatten_xml(xml.LoadHandle(db._.rset:getClob(1)))
            db._.stmt:closeResultSet(db._.rset)
            db._.rset = nil
            local dfields, i = {}
            local nfields = {}
            local col_list = ddl.ROWSET.ROW.TABLE_T.COL_LIST.COL_LIST_ITEM
            if not col_list.__complex then
                col_list = { col_list }
            end
            for i = 1, #col_list do
                local col = col_list[i]
                local row = {
                    Field = col.NAME,
                    Null = (col.NOT_NULL + 0) == 0 and "YES" or "NO",
                    Default = col.DEFAULT_VAL and col.DEFAULT_VAL:gsub("'(.-)' *", "%1") or "",
                    Type = _luadb.oracle.oracle_types[col.TYPE_NUM + 0],
                    Key = "",
                    Extra = "",
                }
                if not row.Type then
                    error("Unknown TYPE_NUM(" .. col.TYPE_NUM .. ") for column " .. row.Field)
                end
                
                if col.PRECISION_NUM and col.SCALE then
                    row.Type = row.Type .. "(" .. col.PRECISION_NUM .. "," .. col.SCALE .. ")"
                elseif col.PRECISION_NUM then
                    row.Type = row.Type .. "(" .. col.PRECISION_NUM .. ")"
                else
                    if row.Type == "NUMBER" and (not col.SCALE or ((col.SCALE + 0) == 0)) then
                        row.Type = "INT"
                    end
                    row.Type = row.Type .. "(" .. col.LENGTH .. ")"
                end
                
                table.insert(dfields, row)
                nfields[row.Field] = row
            end
            
            -- need to add prefix/owner...
            if db:SafeQuery("SELECT USER_CONS_COLUMNS.COLUMN_NAME FROM USER_CONSTRAINTS, USER_CONS_COLUMNS WHERE USER_CONSTRAINTS.TABLE_NAME='" .. db.sql_escape(tbl) .. "' AND CONSTRAINT_TYPE='P' AND USER_CONSTRAINTS.CONSTRAINT_NAME = USER_CONS_COLUMNS.CONSTRAINT_NAME;", "query") ~= 0 then
                error("Unable to retrieve " .. table .. "'s primary keys - error: " .. db:ErrorStr())
            end
            while db._.rset:next() ~= 0 do
                nfields[db._.rset:getString(1)].Key = "PRI"
            end
            
            db._.stmt:closeResultSet(db._.rset)
            db._.rset = nil

            -- need to add prefix/owner...
            if db:SafeQuery("SELECT SEQUENCE_NAME FROM USER_SEQUENCES;", "query") ~= 0 then
                error("Unable to retrieve sequences - error: " .. db:ErrorStr())
            end
            
            local pattern = "^seq_" .. db.sql_escape(tbl) .. "_(%w+)"
            
            while db._.rset:next() ~= 0 do
                local seq_name = db._.rset:getString(1)
                if seq_name:match(pattern) then
                    nfields[(db._.rset:getString(1):gsub(pattern, "%1"))].Extra = "auto_increment"
                end
            end
            
            db._.stmt:closeResultSet(db._.rset)
            db._.rset = nil

            return dfields
        end
    },
}

luadb = {
    mysql = { opendb = function(id, user, password, base, prefix)
        local db
        
--        if user == nil and password == nil and base == nil then
            -- get into a registry to fetch "id"
--        else
--        end
        if type(id) == "table" and type(id._) == "table" then
            user = id._.user
            password = id._.password
            base = id._.base
            prefix = id._.prefix
            id = id._.id
        end
        db = SQLConnection(id, user, password, base)
        return {
            opentable = _luadb.opentable,
            SafeQuery = _luadb.mysql.SafeQuery,
            sql_escape = sql_escape,
            ErrNO = function(db) return db._.conn:ErrNO() end,
            Error = function(db) return db._.conn:Error() end,
            ErrorStr = function(db) return db._.conn:ErrNO() .. " - " .. db._.conn:Error() end,
            Desc = _luadb.mysql.Desc,
            _ = {
                fq = '`',
                eq = '"',
                conn = db,
                id = id,
                user = user,
                password = password,
                base = base,
                prefix = sql_escape(prefix or ""),
                odbc_name = "mysql",
            },
        }
    end, },
    
    oracle = { opendb = function(id, user, password, base, prefix)
        local l_env, conn
        
        if _luadb.oracle.env then
            l_env = _luadb.oracle.env
        else
            l_env = createEnvironment()
            _luadb.oracle.env = l_env
            l_env:setExceptions(false)
        end
        
        if type(id) == "table" and type(id._) == "table" then
            user = id._.user
            password = id._.password
            base = id._.base
            prefix = id._.prefix
            id = id._.id
        end
        conn = l_env:createConnection(user, password, base)
        if not conn then
            return nil, l_env:getErrorCode(), l_env:getErrorMsg()
        end
        return {
            opentable = _luadb.opentable,
            SafeQuery = _luadb.oracle.SafeQuery,
            sql_escape = sql_escape,
            ErrNO = function(db) return db._.errNO end,
            Error = function(db) return db._.errStr end,
            ErrorStr = function(db) return db._.errStr end,
            Desc = _luadb.oracle.Desc,
            _ = {
                fq = '"',
                eq = "'",
                conn = conn,
                id = id,
                user = user,
                password = password,
                base = base,
                prefix = sql_escape(prefix or ""),
                odbc_name = "oracle",
            },
        }
        
    end, },
}

luadb.opendb = luadb.mysql.opendb