Converts an MSSQL database creating script to PostgreSQL. Uses a VBScript implementation of preg_replace for the heavy lifting.

pg_conv.vbs

Option Explicit
Const ForWriting = 2
Const TristateTrue = -1
Dim sFile, sOutputFile, oOutputStream, sText

sFile = WScript.Arguments.Named("i")
sOutputFile = WScript.Arguments.Named("o")
If LenB(sFile) = 0 Then
    WScript.echo "usage: pg_conv.vbs /i:intput_file.sql [/o:output_file.sql]"
    WScript.Quit 1
End If
If LenB(sOutputFile) = 0 Or LCase(sOutputFile) = "con" Then
    Set oOutputStream = WScript.StdOut
Else
    Set oOutputStream = CreateObject("Scripting.FileSystemObject").OpenTextFile(sOutputFile, ForWriting, True, TristateTrue)
End If

sText = ReadFile(sFile)
sText = preg_replace("/^SET\s+NOCOUNT\s+ON$/mi", "-- @@Automatically generated by pg_conv.vbs on " & Now() & "@@", sText)
sText = preg_replace("/(\[|\])/mi", """", sText)
sText = preg_replace("/\s+(NONCLUSTERED|CLUSTERED|COLLATE\s+\w+)/mi", vbNullString, sText)
sText = preg_replace("/,\r\n\tCONSTRAINT/mi", "," & vbCrLf & vbTab & "ADD CONSTRAINT", sText)
sText = preg_replace("/\r\nGO\r\n/mi", ";" & vbCrLf, sText)
sText = preg_replace("/""?\buniqueidentifier\b""?/mi", "uuid", sText)
sText = preg_replace("/""?\bdatetime\b""?/mi", "timestamp", sText)
sText = preg_replace("/""?\btinyint\b""?/mi", "smallint", sText)
sText = preg_replace("/""?\bsmallint\b""?/mi", "smallint", sText)
sText = preg_replace("/""?int""? IDENTITY.*\)/mi", "serial", sText)
sText = preg_replace("/""?\bimage\b""?/mi", "bytea", sText)
sText = preg_replace("/""?\bsysname\b""?/mi", "varchar(128)", sText)
sText = preg_replace("/""?\bnvarchar\b""?/mi", "varchar", sText)
sText = preg_replace("/""?\bbit\b""?/mi", "boolean", sText)
sText = preg_replace("/""?\bdecimal\b""?/mi", "numeric", sText)
sText = preg_replace("/""?\bint\b""?/mi", "integer", sText)
sText = preg_replace("/""?\binteger\b""?/mi", "integer", sText)
sText = preg_replace("/""?\bvarchar\b""?/mi", "varchar", sText)
sText = preg_replace("/""?\bchar\b""?/mi", "char", sText)
sText = preg_replace("/""?\btext\b""?/mi", "text", sText)
sText = preg_replace("/INSERT\t/mi", "INSERT INTO", sText)
sText = preg_replace("/GETDATE\(\)/mi", "now()", sText)
sText = preg_replace("/NEWID\(\)/mi", "uuid_generate_v1()", sText)
sText = preg_replace("/-- { begin_create_stats }/mi", "/* { begin_create_stats } --", sText)
sText = preg_replace("/-- { end_create_stats }/mi", "-- { begin_create_stats } */", sText)
sText = preg_replace("/ADD(\s+)CONSTRAINT\s+([^\r\n]*)\s+DEFAULT\s+([^\r\n]*)\s+FOR\s+([^\r\n]*)([,;])/mi", _
    "$1ALTER COLUMN $4 SET DEFAULT $3$5", sText)
sText = preg_replace_callback("/SET DEFAULT \((0|1)\)/mi", _
    preg_substitute("SET DEFAULT (CAST(\{1} AS boolean))"), sText)
sText = preg_replace_callback("/datediff\(day,0,(""?\w[\w\d]*""?)\) = 0/mi", _
    preg_substitute("(\1 >= TIMESTAMP '1900-01-01' AND \1 < TIMESTAMP '1900-01-02')"), sText)

oOutputStream.Write sText

Private Function preg_init(find_re)
    Set preg_init = New RegExp
    With preg_init
        .Global = True
        If Left(find_re, 1) = "/" Then
            Dim pos: pos = InStrRev(find_re, "/")
            .Pattern = Mid(find_re, 2, pos - 2)
            .IgnoreCase = (InStr(pos, find_re, "i") > 0)
            .Multiline = (InStr(pos, find_re, "m") > 0)
        Else
            .Pattern = find_re
        End If
    End With
End Function

Function preg_match(find_re, text)
    preg_match = preg_init(find_re).Test(text)
End Function

Function preg_replace(find_re, replace_arg, text)
    preg_replace = preg_init(find_re).Replace(text, replace_arg)
End Function

Function preg_split(find_re, text)
    Dim esc: esc = ChrW(&HE1B6) '-- U+E000 to U+F8FF - Private Use Area (PUA)
    preg_split = Split(preg_init(find_re).Replace(text, esc), esc)
End Function

Function preg_replace_callback(find_re, replace_arg, text)
    Dim matches, match, count, offset, retval
    
    Set matches = preg_init(find_re).Execute(text)
    If matches.Count = 0 Then
        preg_replace_callback = text
        Exit Function
    End If
    ReDim retval(matches.Count * (1 - IsObject(replace_arg)))
    For Each match In matches
        With match
            retval(count) = Mid(text, 1 + offset, .FirstIndex - offset)
            count = count + 1
            If IsObject(replace_arg) Then
                retval(count) = replace_arg(match)
                count = count + 1
            End If
            offset = .FirstIndex + .Length
        End With
    Next
    retval(count) = Mid(text, 1 + offset)
    If IsObject(replace_arg) Then
        preg_replace_callback = Join(retval, vbNullString)
    Else
        preg_replace_callback = Join(retval, replace_arg)
    End If
End Function

Function preg_substitute(replace_arg)
    Set preg_substitute = New preg_substitute_class.init(replace_arg)
End Function

Class preg_substitute_class
    private m_esc
    Private m_replace
    
    Public Function init(replace_arg)
        m_esc = ChrW(&HE1B6) '-- U+E000 to U+F8FF - Private Use Area (PUA)
        m_replace = Replace(replace_arg, "\", m_esc)
        Set init = Me
    End Function
    
    Public Default Function callback(match)
        Dim idx, replace_str
        
        replace_str = match.Value
        callback = Replace(Replace(m_replace, m_esc & "{0}", replace_str), m_esc & "0", replace_str)
        With match.SubMatches
            For idx = .Count To 1 Step -1
                replace_str = .Item(idx - 1)
                callback = Replace(Replace(callback, m_esc & "{" & idx & "}", replace_str), m_esc & idx, replace_str)
            Next
        End With
        callback = Replace(callback, m_esc, "\")
    End Function
End Class

Function preg_split_manual(find_re, text)
    Dim matches, match, count, offset, retval
    
    Set matches = preg_init(find_re).Execute(text)
    ReDim retval(matches.Count)
    For Each match In matches
        With match
            retval(count) = Mid(text, 1 + offset, .FirstIndex - offset)
            count = count + 1
            offset = .FirstIndex + .Length
        End With
    Next
    retval(count) = Mid(text, 1 + offset)
    preg_split_manual = retval
End Function

Private Function ReadFile(sFile) 
    Const ForReading = 1
    With CreateObject("Scripting.FileSystemObject")
        ReadFile = .OpenTextFile(sFile, ForReading, False, _
            .OpenTextFile(sFile, ForReading, False, False).Read(2) = Chr(&HFF) & Chr(&HFE)).ReadAll()
    End With
End Function