analyze.patch

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File	+	−
doc/src/sgml/fdwhandler.sgml	0	0
src/backend/commands/analyze.c	0	0
src/include/commands/vacuum.h	0	0

diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
new file mode 100644
index 2c75b80..a78748b
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
*************** AcquireSampleRowsFunc (Relation relation
*** 312,317 ****
--- 312,320 ----
       the table into the output parameters <parameter>totalrows</> and
       <parameter>totaldeadrows</>.  (Set <parameter>totaldeadrows</> to zero
       if the FDW does not have any concept of dead rows.)
+      To avoid excessive size of <parameter>rows</>, all values of variable
+      length can be truncated to length <literal>WIDTH_THRESHOLD+1</> since
+      all such values are discarded during analyze processing.
      </para>
  
      <para>
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
new file mode 100644
index ff27164..5b21f3c
*** a/src/backend/commands/analyze.c
--- b/src/backend/commands/analyze.c
*************** ind_fetch_func(VacAttrStatsP stats, int 
*** 1782,1798 ****
   */
  
  
- /*
-  * To avoid consuming too much memory during analysis and/or too much space
-  * in the resulting pg_statistic rows, we ignore varlena datums that are wider
-  * than WIDTH_THRESHOLD (after detoasting!).  This is legitimate for MCV
-  * and distinct-value calculations since a wide value is unlikely to be
-  * duplicated at all, much less be a most-common value.  For the same reason,
-  * ignoring wide values will not affect our estimates of histogram bin
-  * boundaries very much.
-  */
- #define WIDTH_THRESHOLD  1024
- 
  #define swapInt(a,b)	do {int _tmp; _tmp=a; a=b; b=_tmp;} while(0)
  #define swapDatum(a,b)	do {Datum _tmp; _tmp=a; a=b; b=_tmp;} while(0)
  
--- 1782,1787 ----
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
new file mode 100644
index 3c95dec..2d53a11
*** a/src/include/commands/vacuum.h
--- b/src/include/commands/vacuum.h
*************** extern void lazy_vacuum_rel(Relation one
*** 167,172 ****
--- 167,187 ----
  				BufferAccessStrategy bstrategy);
  
  /* in commands/analyze.c */
+ 
+ /*
+  * To avoid consuming too much memory during analysis and/or too much space
+  * in the resulting pg_statistic rows, we ignore varlena datums that are wider
+  * than WIDTH_THRESHOLD (after detoasting!).  This is legitimate for MCV
+  * and distinct-value calculations since a wide value is unlikely to be
+  * duplicated at all, much less be a most-common value.  For the same reason,
+  * ignoring wide values will not affect our estimates of histogram bin
+  * boundaries very much.
+  * To avoid excessive memory consumption, foreign data wrappers can truncate
+  * any varlena datum in samples returned by an AcquireSampleRowsFunc to
+  * WIDTH_THRESHOLD+1.
+  */
+ #define WIDTH_THRESHOLD  1024
+ 
  extern void analyze_rel(Oid relid, VacuumStmt *vacstmt,
  			BufferAccessStrategy bstrategy);
  extern bool std_typanalyze(VacAttrStats *stats);