• Fixed length fields (this feat may be removed by popular demand).
• ISAM and B+Tree indexing. A note about indexing: I have dropped the idea of doing B+Tree indexing on disk, since the current implementation is ISAM on disk and B+Tree with linked list in memory (which is FASTER than a simple B+Tree).
• string-oriented.
• easy to use.

Use of the RXDBase class

import RXDbase

Is required in your NetRexx source file.

A detailed explanation of all the methods.

Why did I state 'methods', and not also 'properties' or 'exceptions' ?
Simply put, the RXDbase class has no public properties,
and doesn't throw exceptions. Instead, it has methods to find out
if there have been errors, and to query the value of some properties.

Limitations:

• you cannot have currently more than 1000 fields in a record [upped from 256].
• you have to have at least an index.

The default return strings for the following methods are:
DBNOTSTARTED: (can't work on nothing)
READY: (no errors)
SYNTAX ERROR: (go figure)
ERROR:FILE ACCESS PROBLEMS (something weird at file level)

Unless stated otherwise. More error codes will be introduced as
the RXDbase will be enhanced.

Index of available constructors and methods:

RXDbase()

A simple constructor.

RXDbase(Rexx rName, Rexx[,] rRec)

A constructor used to create a database.

RXDbase(Rexx rName)

A constructor used to connect to an existing database.

Rexx addfield(Rexx rFieldName, Rexx rFieldLength, Rexx rFieldIndexingMethod)

Adds a field to the currently opened database.

Rexx connect(Rexx rName, Rexx[,] rRec)

Creates a new database and connects to it.

Rexx connect(Rexx rName)

Connects to an existing database.

Rexx definefilter(Rexx rFilter)

Defines a filter to be used in future loadrec calls.

Rexx delerec(Rexx[] rToDele, boolean bDelete)

Deletes/Undeletes one or more records.

Rexx deletedb(Rexx rDbName)

Deletes a whole database.

Rexx delfield(Rexx rFieldName)

Deletes a field of the currently opened database.

Rexx disconnect()

Disconnects from the currently opened database.

Rexx[, ] getdbinfo()

Gets information about record structure for the currently opened database.

Rexx[] getdbstats()

Gets some useful statistics about the database.

Rexx[] getdbstatus()

Returns the current in use filter and release version for RXDbase.

Rexx globalrebuildidx()

Rebuilds all of the indexes.

Rexx[, ] loadrec(Rexx rIdx, Rexx rHowManyRec, Rexx rStart, boolean bForward)

Loads a set of records.

Rexx[, ] loadrecwithfilter(Rexx rIdx, Rexx rHowManyRec, Rexx rStart, boolean bForward, Rexx rFilter)

Loads a set of records according to a temporary filter.

Rexx modfieldidx(Rexx rFieldName, Rexx rFieldIndexingMethod)

Modifies (on the fly) indexing strategy for a field.

Rexx modfieldlength(Rexx rFieldName, Rexx rNewLength)

Modifies (on the fly) the length of a field.

Rexx modfieldname(Rexx rOldName, Rexx rNewName)

Modifies (on the fly) the name of a field.

Rexx modirec(Rexx[, ] rToModi)

Modifies one or more records.

Rexx pack()

Packs the database (physically purge deleted records).

Rexx rebuildidx(Rexx rFieldName)

Rebuilds the index for a single field.

Rexx saverec(Rexx[, ] rToSave, Rexx rMode)

Stores one or more records in the database.

Rexx status()

Returns the current error status of the database.

The following constructors are available for the RXDbase class:

RXDbase()
RXDbase(Rexx rName, Rexx[, ] rRec)
RXDbase(Rexx rName)

The above two constructors works as in the CONNECT method (see below).

The following methods can be issued on the RXDbase class:

Rexx addfield(Rexx rFieldName, Rexx rFieldLength, Rexx rFieldIndexingMethod)

With this method you can add a field to a database; you can also specify an index, which will be built automatically for you.

Notes: Don't use names already in use in the same database, and specify a valid indexing method (currently supported: "ISAMxx" and "NONEx"); The new fields' contents will be blank for all records (of course). See the "connect" method for a listing of valid XX, X values.

Rexx connect(Rexx rName, Rexx[, ] rRec)
This method is the very first to issue, if you have not instantiated an RXDbase variable with the two-parameters or one-parameter constructor. If you have, you can omit this method.

rName is the name of the file without any extension that is hosting/will host the database on the disk. RXDbase will add the file name extension '.dat' to this name.

rRec is a bi-dimensional Rexx array that has to be built this way:
rRec[0, 0] --> Number of fields in the database.
rRec[n, 0] --> Length (a whole number stored in a Rexx variable) of field 'n'.
rRec[n, 1] --> Name of field 'n' (it will be used later).
rRec[n, 2] --> Indexing method of the field: it can be any of the following:
ISAM = Indexed Sequential Access Method, good if you need
to work on the database ordered on this field. Actually, the current implementation of the indexes is something like ISAM + B+Trees, but the name ISAM has been kept for compatibility.
NONE = when you don't do much operations on this field.

More on the indexing: if you want a field not to allow null values or duplicate
values, you should append an '1' or a '0' to the indexing string like here:

ISAM00 = ISAM indexing, duplicate and null values are allowed.
ISAM11 = ISAM indexing, duplicate and null values are NOT allowed.
ISAM10 = ISAM indexing, duplicate values are NOT allowed, null values are.
ISAM01 = ISAM indexing, duplicate values are allowed, null values are NOT.
NONE0 = No indexing, null values are allowed.
NONE1 = No indexing, null values are NOT allowed.

As you may have noticed, you cannot specify 'no duplicate values' for the no-index strategy of indexing.

Notes:

• you cannot have currently more than 1000 fields in a record.

• you have to have at least an index.

• when you create a database, several files will be created.

• One, .dat is the real data base; then, you have a file for every index. This was done for speed.

Rexx connect(Rexx rName)

This method simply connects to an existing database (rName is the name of the file).

Rexx definefilter(Rexx rFilter)

By means of this method you can specify a filter with which all subsequent loadrec calls will have to comply.

Parameters:

rFilter = an expression, which can have nested expressions in parenthesis. Separate filter conditions with | (OR condition) and & (AND condition).

Example: name = rob* | surname = kol* will search for every person whose name starts with 'rob' or whose surname starts with 'kol'.

Note:
Valid filter conditions are:
<fieldname> <operator> <value>

Where <fieldname> is a valid field name, e.g. 'Name'.
<operator> can be one of the following: =,<>,>,>=,<,<=
<value> is a valid value for that field, e.g. 'Robert'

Wildcards are allowed only for the = and <> operators, and they are represented by the symbol '*', which means "every number of any character". So, Ro* can be Robert, Ronald, etc. *t can be Matt, Robert, etc.
M*t can be Matt, mount, etc. (The search is always case-insensitive)
You can use only one '*' on a given filter (e.g. you can't query for "Name = *u*i*l*"), with the notable exception of the form *value*, which means "find a substring anywhere that is equal to 'value'".

Example: "Telephone = *555*" will search for all phone numbers with a 555 in them.

Your filter conditions will not produce anything until the next LOADREC method is issued, from them on all the calls to LOADREC will use your filter. When requesting records, if a filter condition is present, the information about the absolute position on the index of the records will not be meaningful.
If you specify a filter condition when another one is in use, the first one will be dropped, and the most recent one will be used.
Passing the null string or the "" value will reset the filter conditions.

Rexx delerec(Rexx[] rToDele, boolean bDelete)

Delerec is used to delete/undelete one or more records.

rToDele[0] has to be the total number of records to be (un)deleted, and rToDele[n] is the ACTUAL position of the n-th record to be (un)deleted on the database (NOT A NUMBER RELATIVE TO AN INDEX).
The first record on the database is 1 (one).

When bDelete = 1, the records are to be deleted,
when bDelete = 0, the records are to be undeleted.

No errors will come by deleting an already deleted record, or the other way around. Modirec returns one of the standard RXDbase error codes.

Rexx deletedb(Rexx rDbName)

This method deletes an entire database, indexes and all.

Rexx delfield(Rexx rFieldName)

With this method you can delete a field from a database, including indexes (if any).

Note: As ever, rFieldName can be the name of the field (ie, 'name') or the number which references the field (ie, '4', if the fourth field is 'name'). Warning: The field will disappear *physically* from the archive. No undo, no restore, zippo.

Rexx disconnect()

Simply put, this method closes all the db activities for the database being used.

Rexx[, ] getdbinfo()

This method returns the database structure (names and field length, along with the number of fields).

The returned values are: (let's say we stored the contents in rRec[, ])

rRec[0, 0] --> Number of fields in the database.
rRec[n, 0] --> Length (a whole number stored in a Rexx variable) of field 'n'.
rRec[n, 1] --> Name of field 'n'.
rRec[n, 2] --> Indexing method of the field: it can be any of the following:
ISAMXX = Indexed Sequential Access Method, good if you need to work on the database ordered on this field. Actually, the current implementation of the indexes is something like ISAM + B+Trees, but the name ISAM has been kept for compatibility.
XX = 00, 01, 10, 11.
NONEX = when you don't do much operations on this field.
X = 0, 1.
See the "connect" method for a listing of valid XX, X values.

Rexx[] getdbstats()

This method returns some useful statistics about the database.

This function returns an array in which:

Element 0 of the array is the db size in bytes.
Element 1 is the record size in bytes.
Element 2 is the total number of records in the database.
Element 3 is the number of active records (not marked with 'N') in the database.

Rexx[] getdbstatus()

This method lets you retrieve the RXDbase revision and the presence of a filter.

Returns:
rVar[0] = "No Filter" or "Filter Present" or "No DB loaded"
rVar[1] = RXDbase version number (e.g. "RXDbase 1.0 Max Marsiglietti 1997").

Rexx globalrebuildidx()

With this method you can rebuild all the indexes of the database currently in use. Useful to correct errors, or to restore all the indexes after a backup+restore. (This way if you need to backup your archives, you can backup only the .dat file, and issueing the globalrebuildidx method after the restore you will get back all of your indexes).

Rexx[, ] loadrec(Rexx rIdx, Rexx rHowManyRec, Rexx rStart, boolean bForward)

Loadrec loads in memory a number of records from the database. If a filter has been defined with the definefilter method, it will be used; otherwise, no record filtering will occur.

rIdx is an existing index; the returned records will be ordered on it. It can be a number (i.e. rIdx = 1 means 'the index on the first field') or a name (that field's EXACT name, i.e. "Name").
rHowManyRec is the number of the records to be loaded, ie '72'. It can also have the value 'ALL', meaning you want all of the records from rStart on.
rStart is the starting record. The first record is labeled '1'. A valid value for this variable is also 'LAST', which means 'the first record to get is the last in the archive'.
bForward If "true", it means take rHowManyRec records starting from rStart on (ascending order), else it means take them from rStart back (descending order).

It returns a bidimensional array which is structured this way:

rArray[0,0] is the number of records that satisfy the filter condition(s).
rArray[0,1] is the number of records which are actually being returned.
rArray[n,m] is the field n of record m (m = 1 to rArray[0,0]).
rArray[N+1, m] can be "Y" or "N", depending on the given record: "Y" means active, "N" means deleted (only active records are returned, as of this release).
rArray[N+2, m] is the position of the m-th record on the archive (NOT on the index).
rArray[N+3, m] is the position of the m-th record on the used index (NOT on the archive); this information is meaningless if a filter is present.

Rexx[,] loadrecwithfilter(Rexx rIdx, Rexx rHowManyRec, Rexx rStart, boolean bForward, Rexx rFilter)

This method lets you perform a loadrec with a certain filter, then reset the filter to whatever it was before.

The parameters exactly match the ones in methods loadrec and definefilter.

Rexx modfieldidx(Rexx rFieldName, Rexx rFieldIndexingMethod)

Modfieldidx lets you modify the indexing method for a given, existing, field. It automatically rebuilds the index, if passing from no index to some kind of index. It is useful if you decide that you don't need anymore an index, or if you think that you should have put an index on a field at database definion time, but you didn't.

Note: rFieldIndexingMethod can be one of the following: "ISAMXX", "NONEX". See the "connect" method for a listing of valid XX, X values.

Rexx modfieldlength(Rexx rFieldName, Rexx rNewLength)

This method lets you change the length of a field.

Note: All the information in excess of the new length will be lost.
Note2: As ever, rFieldName can be a number (eg. '4' meaning the 4th field) or a name (eg. "surname").

Rexx modfieldname(Rexx rOldName, Rexx rNewName)

This method lets you change the name of a field.

The field with name rOldName will get rNewName name.
Note: rOldName can be a number (eg. '4' meaning the 4th field) or a name (eg. "surname").

Rexx modirec(Rexx[, ] rToModi)

Modirec is used to modify one or more records in the database.

rToModi is to be built this way:

rToModi[0, 0] is the total number of records to be modified
rToModi[n, m] is field n of the m-th record to be modified. n and m always start from 1 (one).
rToModi[0, m] is the ACTUAL number of the record in the database (NOT A NUMBER RELATIVE TO AN INDEX) to be overwritten. This information is the same of the [N+2, m] element in the loadrec method. The first record in the database is marked as '1'.

Warning: this method doesn't update single fields, it overwrites whole records.

Note: there is not an order on the records to be modified, i.e. you can have:

rToModi[0, 1] = 5
rToModi[0, 2] = 3
rToModi[0, 3] = 18

Returns:

An appropriate error message is returned in case of errors, else you will be returned a Rexx string, in which every character is either '0' or '1', where '0' means that the specified record was not succesfully saved (a null value where nulls weren't allowed, or a duplicate value where there sholdn't be any) and a '1' means that the record was succesfully saved.
Example:
If we try to save 3 records and we get '010' back from modirec, this means that only the 2nd record among the ones passed to modirec was succesfully stored in the database: the remaining two were discarded (probably because they had duplicated values for fields in which we specified that no duplicate values should be allowed).

Rexx pack()

When you delete a record by means of the DELEREC function, that record doesn't physically get deleted from the archive, it is instead marked as 'deleted'.
PACK does what the name suggests, it permanently deletes records from the archive, updating automatically all the indexes.

Rexx rebuildidx(Rexx rFieldName)

This method is similar to globalrebuildidx, but must be invoked explicitly on an index.

Note: As ever, rFieldName can be the name of the field (ie, 'name') or the number which references the field (ie, '4', if the fourth field is 'name').

Rexx saverec(Rexx[, ] rToSave, Rexx rMode)

This method lets you write one or more records on disk. All of the indexes are automatically updated.

rMode can only be 'overwrite' or 'append' (case isn't significative).

rToSave is to be built this way:
rToSave[0,0] --> number of records to be written.
rToSave[n,m] --> field n of record m.

Warning: both n,m are to start from 1 (one).
Warning: When you specify 'overwrite', the whole database will be overwritten (deleted), and the indexes will be resetted.

Returns:

An appropriate error message is returned in case of errors, else you will be returned a Rexx string, in which every character is either '0' or '1', where '0' means that the specified record was not succesfully saved (a null value where nulls weren't allowed, or a duplicate value where there sholdn't be any) and a '1' means that the record was saved succesfully.
Example:
If we try to save 3 records and we get '010' back from saverec, this means that only the 2nd record among the ones passed to saverec was succesfully stored in the database: the remaining two were discarded (probably because they had duplicated values for fields in which we specified that no duplicate values should be allowed).

Rexx status()

With this method, you can query the internal status of the database.
Possible return values are:
DBNOTSTARTED: (can't work on nothing)
READY: (no errors)
SYNTAX ERROR: (go figure)
ERROR:FILE ACCESS PROBLEMS (something weird at file level)

History

1.16 -- Corrected a problem with large databases.. [03-mar-98]
1.15 -- Corrected a concurrency problem, added automatical DB closing when another DB is opened, corrected problems with loadrec and no filters present, improved query performances. [25-jan-98]
1.14 -- Revised corrupted archive recovery. [12-jan-98]
1.13 -- Added stricter parameter checking for loadrec. [7-jan-98]
1.12 -- Improved the filtering capabilities and performances.[31-dec-97]
1.10 -- Upgraded RXDbase to Java 1.1 [12-dec-97]
1.07 -- Corrected: other minor filter failures. Speeded up filter operations, multithreaded the whole class (speeded up the saverec/modirec/delerec operations). [01-jun-1997]
1.06 -- Corrected: Minor filter failures. Speeded up filter operations. [26-may-1997]
1.05 -- Corrected the NODUPLICATES behaviour: now also records in the middle of an archive are correctly checked for duplicate values. [16-may-97]
1.04 -- Corrected an error on search functions (weren't case-insensitive). [14-may-97]
1.03 -- Corrected an error on index handling. [8-may-97]
1.02 -- Corrected errors in the dbf to dat utilities; Updated online reference; Enhanced installation program; added .dbf conversion on MaxBase startup; added automatical rebuild of indexes on MaxBase startup (only when necessary). (4-may-97)
1.01 -- Added information for registering the software with BTM Micro; corrected a small bug with indexes (2-may-1997).
1.00 -- Initial release (2-may-1997).