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(slib.info)Base Table
Base Table ========== A base table implementation using Scheme association lists is available as the value of the identifier `alist-table' after doing: `(require 'alist-table)' Association list base tables are suitable for small databases and support all Scheme types when temporary and readable/writeable Scheme types when saved. I hope support for other base table implementations will be added in the future. This rest of this section documents the interface for a base table implementation from which the Note: Relational Database package constructs a Relational system. It will be of interest primarily to those wishing to port or write new base-table implementations. All of these functions are accessed through a single procedure by calling that procedure with the symbol name of the operation. A procedure will be returned if that operation is supported and `#f' otherwise. For example: (require 'alist-table) (define open-base (alist-table 'make-base)) make-base => *a procedure* (define foo (alist-table 'foo)) foo => #f - Function: make-base filename key-dimension column-types Returns a new, open, low-level database (collection of tables) associated with FILENAME. This returned database has an empty table associated with CATALOG-ID. The positive integer KEY-DIMENSION is the number of keys composed to make a PRIMARY-KEY for the catalog table. The list of symbols COLUMN-TYPES describes the types of each column for that table. If the database cannot be created as specified, `#f' is returned. Calling the `close-base' method on this database and possibly other operations will cause FILENAME to be written to. If FILENAME is `#f' a temporary, non-disk based database will be created if such can be supported by the base table implelentation. - Function: open-base filename mutable Returns an open low-level database associated with FILENAME. If MUTABLE? is `#t', this database will have methods capable of effecting change to the database. If MUTABLE? is `#f', only methods for inquiring the database will be available. If the database cannot be opened as specified `#f' is returned. Calling the `close-base' (and possibly other) method on a MUTABLE? database will cause FILENAME to be written to. - Function: write-base lldb filename Causes the low-level database LLDB to be written to FILENAME. If the write is successful, also causes LLDB to henceforth be associated with FILENAME. Calling the `close-database' (and possibly other) method on LLDB may cause FILENAME to be written to. If FILENAME is `#f' this database will be changed to a temporary, non-disk based database if such can be supported by the underlying base table implelentation. If the operations completed successfully, `#t' is returned. Otherwise, `#f' is returned. - Function: sync-base lldb Causes the file associated with the low-level database LLDB to be updated to reflect its current state. If the associated filename is `#f', no action is taken and `#f' is returned. If this operation completes successfully, `#t' is returned. Otherwise, `#f' is returned. - Function: close-base lldb Causes the low-level database LLDB to be written to its associated file (if any). If the write is successful, subsequent operations to LLDB will signal an error. If the operations complete successfully, `#t' is returned. Otherwise, `#f' is returned. - Function: make-table lldb key-dimension column-types Returns the BASE-ID for a new base table, otherwise returns `#f'. The base table can then be opened using `(open-table LLDB BASE-ID)'. The positive integer KEY-DIMENSION is the number of keys composed to make a PRIMARY-KEY for this table. The list of symbols COLUMN-TYPES describes the types of each column. - Constant: catalog-id A constant BASE-ID suitable for passing as a parameter to `open-table'. CATALOG-ID will be used as the base table for the system catalog. - Function: open-table lldb base-id key-dimension column-types Returns a HANDLE for an existing base table in the low-level database LLDB if that table exists and can be opened in the mode indicated by MUTABLE?, otherwise returns `#f'. As with `make-table', the positive integer KEY-DIMENSION is the number of keys composed to make a PRIMARY-KEY for this table. The list of symbols COLUMN-TYPES describes the types of each column. - Function: kill-table lldb base-id key-dimension column-types Returns `#t' if the base table associated with BASE-ID was removed from the low level database LLDB, and `#f' otherwise. - Function: make-keyifier-1 type Returns a procedure which accepts a single argument which must be of type TYPE. This returned procedure returns an object suitable for being a KEY argument in the functions whose descriptions follow. Any 2 arguments of the supported type passed to the returned function which are not `equal?' must result in returned values which are not `equal?'. - Function: make-list-keyifier key-dimension types The list of symbols TYPES must have at least KEY-DIMENSION elements. Returns a procedure which accepts a list of length KEY-DIMENSION and whose types must corresopond to the types named by TYPES. This returned procedure combines the elements of its list argument into an object suitable for being a KEY argument in the functions whose descriptions follow. Any 2 lists of supported types (which must at least include symbols and non-negative integers) passed to the returned function which are not `equal?' must result in returned values which are not `equal?'. - Function: make-key-extractor key-dimension types column-number Returns a procedure which accepts objects produced by application of the result of `(make-list-keyifier KEY-DIMENSION TYPES)'. This procedure returns a KEY which is `equal?' to the COLUMN-NUMBERth element of the list which was passed to create COMBINED-KEY. The list TYPES must have at least KEY-DIMENSION elements. - Function: make-key->list key-dimension types Returns a procedure which accepts objects produced by application of the result of `(make-list-keyifier KEY-DIMENSION TYPES)'. This procedure returns a list of KEYs which are elementwise `equal?' to the list which was passed to create COMBINED-KEY. In the following functions, the KEY argument can always be assumed to be the value returned by a call to a _keyify_ routine. In contrast, a MATCH-KEYS argument is a list of length equal to the number of primary keys. The MATCH-KEYS restrict the actions of the table command to those records whose primary keys all satisfy the corresponding element of the MATCH-KEYS list. The elements and their actions are: `#f' The false value matches any key in the corresponding position. an object of type procedure This procedure must take a single argument, the key in the corresponding position. Any key for which the procedure returns a non-false value is a match; Any key for which the procedure returns a `#f' is not. other values Any other value matches only those keys `equal?' to it. The KEY-DIMENSION and COLUMN-TYPES arguments are needed to decode the combined-keys for matching with MATCH-KEYS. - Function: for-each-key handle procedure key-dimension column-types match-keys Calls PROCEDURE once with each KEY in the table opened in HANDLE which satisfy MATCH-KEYS in an unspecified order. An unspecified value is returned. - Function: map-key handle procedure key-dimension column-types match-keys Returns a list of the values returned by calling PROCEDURE once with each KEY in the table opened in HANDLE which satisfy MATCH-KEYS in an unspecified order. - Function: ordered-for-each-key handle procedure key-dimension column-types match-keys Calls PROCEDURE once with each KEY in the table opened in HANDLE which satisfy MATCH-KEYS in the natural order for the types of the primary key fields of that table. An unspecified value is returned. - Function: delete* handle key-dimension column-types match-keys Removes all rows which satisfy MATCH-KEYS from the table opened in HANDLE. An unspecified value is returned. - Function: present? handle key Returns a non-`#f' value if there is a row associated with KEY in the table opened in HANDLE and `#f' otherwise. - Function: delete handle key Removes the row associated with KEY from the table opened in HANDLE. An unspecified value is returned. - Function: make-getter key-dimension types Returns a procedure which takes arguments HANDLE and KEY. This procedure returns a list of the non-primary values of the relation (in the base table opened in HANDLE) whose primary key is KEY if it exists, and `#f' otherwise. - Function: make-putter key-dimension types Returns a procedure which takes arguments HANDLE and KEY and VALUE-LIST. This procedure associates the primary key KEY with the values in VALUE-LIST (in the base table opened in HANDLE) and returns an unspecified value. - Function: supported-type? symbol Returns `#t' if SYMBOL names a type allowed as a column value by the implementation, and `#f' otherwise. At a minimum, an implementation must support the types `integer', `symbol', `string', `boolean', and `base-id'. - Function: supported-key-type? symbol Returns `#t' if SYMBOL names a type allowed as a key value by the implementation, and `#f' otherwise. At a minimum, an implementation must support the types `integer', and `symbol'. `integer' Scheme exact integer. `symbol' Scheme symbol. `boolean' `#t' or `#f'. `base-id' Objects suitable for passing as the BASE-ID parameter to `open-table'. The value of CATALOG-ID must be an acceptable `base-id'.
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