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<P>Slide 73 of 102</P>
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<H2>Web DBI - Browsing pages of results</H2>
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<LI><H2>Re-execute query each time then count/discard (simple but expensive)
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<LI>works well for small cheap results sets or where users rarely view many pages
<LI>fast initial response, degrades gradually for later pages
<LI>count/discard in server is better but still inefficient for large result sets
<LI>count/discard affected by inserts and deletes from other processes
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<LI><H2>Re-execute query with where clause using min/max keys from last results
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<LI>works well where original query can be qualified in that way
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<LI><H2>Select and cache full result rows somewhere for fast access
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<LI>can be expensive for large result sets with big fields
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<LI><H2>Select and cache only the row keys, fetch full rows as needed
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<LI>optimisation of above, use ROWID if supported, "select
where key in (
)"
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<LI><H2>If data is static and queries predictable
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<LI>then custom pre-built indexes may be useful
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<LI><H2>The caches can be stored...
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<LI>on web server, e.g., using DBM file with locking (see also spread)
<LI>on database server, e.g., using a table keyed by session id</UL></UL></P>
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