I found this over on the PostgreSQL website FAQ:

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4.4) What is the maximum size for a row, a table, and a database?

These are the limits:

Maximum size for a database? unlimited (32 TB databases exist)
Maximum size for a table? 32 TB
Maximum size for a row? 1.6TB
Maximum size for a field? 1 GB
Maximum number of rows in a table? unlimited
Maximum number of columns in a table? 250-1600 depending on column types
Maximum number of indexes on a table? unlimited

Of course, these are not actually unlimited, but limited to available disk space and memory/swap space. Performance may suffer when these values get unusually large.

The maximum table size of 32 TB does not require large file support from the operating system. Large tables are stored as multiple 1 GB files so file system size limits are not important.

The maximum table size and maximum number of columns can be quadrupled by increasing the default block size to 32k.

One limitation is that indexes can not be created on columns longer than about 2,000 characters. Fortunately, such indexes are rarely needed. Uniqueness is best guaranteed by a funtion index of an MD5 hash of the long column, and full text indexing allows for searching of words within the column.

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Regards,

LelandJ