I686LINUX/util/I686LINUX/doc/postgresql/html/pltcl-unknown.html

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  94 ><A
  95 NAME="PLTCL-UNKNOWN"
  96 >38.7. Modules and the <CODE
  97 CLASS="FUNCTION"
  98 >unknown</CODE
  99 > command</A
 100 ></H1
 101 ><P
 102 >       PL/Tcl has support for autoloading Tcl code when used.
 103         It recognizes a special table, <TT
 104 CLASS="LITERAL"
 105 >pltcl_modules</TT
 106 >, which
 107         is presumed to contain modules of Tcl code.  If this table
 108         exists, the module <TT
 109 CLASS="LITERAL"
 110 >unknown</TT
 111 > is fetched from the table
 112         and loaded into the Tcl interpreter immediately after creating
 113         the interpreter.
 114        </P
 115 ><P
 116 >        While the <TT
 117 CLASS="LITERAL"
 118 >unknown</TT
 119 > module could actually contain any
 120         initialization script you need, it normally defines a Tcl
 121         <CODE
 122 CLASS="FUNCTION"
 123 >unknown</CODE
 124 > procedure that is invoked whenever Tcl does
 125         not recognize an invoked procedure name.  <SPAN
 126 CLASS="APPLICATION"
 127 >PL/Tcl</SPAN
 128 >'s standard version
 129         of this procedure tries to find a module in <TT
 130 CLASS="LITERAL"
 131 >pltcl_modules</TT
 132 >
 133         that will define the required procedure.  If one is found, it is
 134         loaded into the interpreter, and then execution is allowed to
 135         proceed with the originally attempted procedure call.  A
 136         secondary table <TT
 137 CLASS="LITERAL"
 138 >pltcl_modfuncs</TT
 139 > provides an index of
 140         which functions are defined by which modules, so that the lookup
 141         is reasonably quick.
 142        </P
 143 ><P
 144 >        The <SPAN
 145 CLASS="PRODUCTNAME"
 146 >PostgreSQL</SPAN
 147 > distribution includes
 148         support scripts to maintain these tables:
 149         <TT
 150 CLASS="COMMAND"
 151 >pltcl_loadmod</TT
 152 >, <TT
 153 CLASS="COMMAND"
 154 >pltcl_listmod</TT
 155 >,
 156         <TT
 157 CLASS="COMMAND"
 158 >pltcl_delmod</TT
 159 >, as well as source for the standard
 160         <TT
 161 CLASS="LITERAL"
 162 >unknown</TT
 163 > module in <TT
 164 CLASS="FILENAME"
 165 >share/unknown.pltcl</TT
 166 >.  This module
 167         must be loaded
 168         into each database initially to support the autoloading mechanism.
 169        </P
 170 ><P
 171 >        The tables <TT
 172 CLASS="LITERAL"
 173 >pltcl_modules</TT
 174 > and <TT
 175 CLASS="LITERAL"
 176 >pltcl_modfuncs</TT
 177 >
 178         must be readable by all, but it is wise to make them owned and
 179         writable only by the database administrator.
 180        </P
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