Add command for explaining PostgreSQL queries in a format suitable fo…

…r PEV

See http://tatiyants.com/pev/

lisp/init-sql.el

@@ -48,6 +48,68 @@ Fix for the above hasn't been released as of Emacs 25.2."
 (add-hook 'sql-interactive-mode-hook 'sanityinc/font-lock-everything-in-sql-interactive-mode)
 
 
+
+(defun sanityinc/sql-explain-region-as-json (beg end &optional copy)
+ "Explain the SQL between BEG and END in detailed JSON format.
+This is suitable for pasting into tools such as
+http://tatiyants.com/pev/.
+
+When the prefix argument COPY is non-nil, do not display the
+resulting JSON, but instead copy it to the kill ring.
+
+If the region is not active, uses the current paragraph, as per
+`sql-send-paragraph'.
+
+Connection information is taken from the special sql-* variables
+set in the current buffer, so you will usually want to start a
+SQLi session first, or otherwise set `sql-database' etc."
+ (interactive "rP")
+ (unless (eq sql-product 'postgres)
+ (user-error "This command is for PostgreSQL only"))
+ (unless (use-region-p)
+ (setq beg (save-excursion
+ (backward-paragraph)
+ (point))
+ end (save-excursion
+ (forward-paragraph)
+ (point))))
+ (let ((query (buffer-substring-no-properties beg end)))
+ (with-current-buffer (if (sql-buffer-live-p sql-buffer)
+ sql-buffer
+ (current-buffer))
+ (let* ((process-environment
+ (append (list (concat "PGDATABASE=" sql-database)
+ (concat "PGHOST=" sql-server)
+ (concat "PGUSER=" sql-user))
+ process-environment))
+ (out-buffer (get-buffer-create "*sql-explain-json*"))
+ (args (list "--no-psqlrc"
+ "-qAt"
+ "-w" ; Never prompt for password
+ "-E"
+ "-c" (concat "EXPLAIN (ANALYZE, COSTS, VERBOSE, BUFFERS, FORMAT JSON) " query ";")
+ ))
+ (err-file (make-temp-file "sql-explain-json")))
+ (with-current-buffer out-buffer
+ (delete-region (point-min) (point-max)))
+ (let ((retcode (apply 'call-process sql-postgres-program nil (list out-buffer err-file) nil args)))
+ (if (zerop retcode)
+ (with-current-buffer out-buffer
+ (json-mode)
+ (if copy
+ (progn
+ (kill-ring-save (buffer-substring-no-properties (point-min) (point-max)))
+ (message "EXPLAIN output copied to kill-ring."))
+ (display-buffer (current-buffer))))
+ (display-buffer (with-current-buffer (get-buffer-create "*sql-explain-errors*")
+ (insert-file-contents err-file nil nil nil t)
+ (current-buffer)))
+ (error "Explain failed")))))))
+
+
+
+
+
 (after-load 'page-break-lines
  (push 'sql-mode page-break-lines-modes))