140 lines
7 KiB
Clojure
140 lines
7 KiB
Clojure
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;; copyright (c) 2019 Sean Corfield, all rights reserved
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(ns next.jdbc.middleware
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"Middleware to wrap SQL operations and result set builders.
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Can wrap a connectable such that you can: supply 'global' options for all
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SQL operations on that connectable; pre-process the SQL and/or parameters
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and/or the options; post-process the result set object (and options);
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post-process each row as it is built; post-process the whole result set.
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The following options can be used to provide those hook functions:
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* :pre-execute-fn -- pre-process the SQL & parameters and options
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returns pair of (possibly updated) SQL & parameters
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and (possibly updated) options
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* (execute SQL)
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* :post-execute-fn -- post-process the result set and options
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returns pair of (possibly updated) `ResultSet` object
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and (possibly updated) options
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* :row!-fn -- post-process each row (and is also passed options)
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returns (possibly updated) row data
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* :rs!-fn -- post-process the whole result set (and is also
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passed options)
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returns (possibly updated) result set data
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The default for all of these is to simply return data unchanged. For
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`:pre-execute-fn` and `:post-execute-fn`, that means returning a pair of
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`[sql-param options]` and `[rs options]` respectively. For `:row!-fn`,
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that means returning the row data unchanged (and ignoring the options).
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For `:rs!-fn`, that means returning the result set data unchanged (and
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ignoring the options).
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For timing middleware, you can pass per-operation timing data through the
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options hash map, so you can measure the timing for the SQL execution, and
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also the time taken to build the full result set (if it is built).
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For logging middleware, you get access to the SQL & parameters prior to
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the execution and the full result set (if it is built).
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You can also transform the SQL & parameters prior to execution and transform
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the rows and/or result set after each is built."
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(:require [next.jdbc.protocols :as p]
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[next.jdbc.result-set :as rs]))
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(defn post-processing-adapter
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"Given a builder function (e.g., `as-lower-maps`), return a new builder
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function that post-processes rows and the result set. The options may
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contain post-processing functions that are called on each row and on the
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the result set. The options map is provided as a second parameter to these
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functions, which should include `:next.jdbc/sql-params` (the vector of SQL
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and parameters, in case post-processing needs it):
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* `:post-execute-fn` -- called on the `ResultSet` object and the options
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immediately after the SQL operation completes
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returns a pair of a (possibly updated) `ResultSet`
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object and (possibly updated) options
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* `:row!-fn` -- called on each row and the options, as the row is
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fully-realized and returns the (possiblly updated)
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row data
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* `:rs!-fn` -- called on the whole result set and the options, as
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the result set is fully-realized and returns the
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(possibly updated) result set data
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The results of these functions are returned as the rows/result set."
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[builder-fn]
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(fn [rs opts]
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(let [exec-fn (get opts :post-execute-fn vector)
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;; rebind both the ResultSet object and the options
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[rs opts] (exec-fn rs opts)
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mrsb (builder-fn rs opts)
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row!-fn (get opts :row!-fn (comp first vector))
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rs!-fn (get opts :rs!-fn (comp first vector))]
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(reify
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rs/RowBuilder
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(->row [this] (rs/->row mrsb))
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(column-count [this] (rs/column-count mrsb))
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(with-column [this row i] (rs/with-column mrsb row i))
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(row! [this row] (row!-fn (rs/row! mrsb row) opts))
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rs/ResultSetBuilder
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(->rs [this] (rs/->rs mrsb))
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(with-row [this mrs row] (rs/with-row mrsb mrs row))
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(rs! [this mrs] (rs!-fn (rs/rs! mrsb mrs) opts))))))
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(defrecord JdbcMiddleware [db global-opts]
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p/Executable
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(-execute [this sql-params opts]
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(let [opts (merge global-opts opts)
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pre-execute-fn (get opts :pre-execute-fn vector)
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;; rebind both the SQL & parameters and the options
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[sql-params opts] (pre-execute-fn sql-params opts)
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builder-fn (get opts :builder-fn rs/as-maps)]
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(p/-execute db sql-params
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(assoc opts
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:builder-fn (post-processing-adapter builder-fn)
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:next.jdbc/sql-params sql-params))))
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(-execute-one [this sql-params opts]
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(let [opts (merge global-opts opts)
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pre-execute-fn (get opts :pre-execute-fn vector)
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;; rebind both the SQL & parameters and the options
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[sql-params opts] (pre-execute-fn sql-params opts)
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builder-fn (get opts :builder-fn rs/as-maps)]
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(p/-execute-one db sql-params
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(assoc opts
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:builder-fn (post-processing-adapter builder-fn)
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:next.jdbc/sql-params sql-params))))
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(-execute-all [this sql-params opts]
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(let [opts (merge global-opts opts)
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pre-execute-fn (get opts :pre-execute-fn vector)
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;; rebind both the SQL & parameters and the options
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[sql-params opts] (pre-execute-fn sql-params opts)
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builder-fn (get opts :builder-fn rs/as-maps)]
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(p/-execute-all db sql-params
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(assoc opts
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:builder-fn (post-processing-adapter builder-fn)
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:next.jdbc/sql-params sql-params)))))
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(defn wrapper
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"Given a connectable, return a wrapped connectable that will run hooks.
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Given a connectable and a hash map of options, return a wrapped connectable
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that will use those options as defaults for any SQL operations and will
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run hooks.
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The following hooks are supported:
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* :pre-execute-fn -- pre-process the SQL & parameters and options
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returns pair of (possibly updated) SQL & parameters
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and (possibly updated) options
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* :post-execute-fn -- post-process the result set and options
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returns pair of (possibly updated) `ResultSet` object
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and (possibly updated) options
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* :row!-fn -- post-process each row (and is also passed options)
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returns (possibly updated) row data
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* :rs!-fn -- post-process the whole result set (and is also
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passed options)
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returns (possibly updated) result set data
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Uses `next.jdbc.middleware/post-processing-adapter for the last three,
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wrapped around whatever `:builder-fn` you supply for each SQL operation."
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([db] (JdbcMiddleware. db {}))
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([db opts] (JdbcMiddleware. db opts)))
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