tableam: Move heap-specific logic from needs_toast_table below tableam.

This allows table AMs to completely suppress TOAST table creation, or
to modify the conditions under which they are created.

Patch by me.  Reviewed by Andres Freund.

Discussion: http://postgr.es/m/CA+Tgmoa4O2n=yphqD2pERUnYmUO84bH1SqMsA-nSxBGsZ7gWfA@mail.gmail.com

diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index 8d8161fd9717f6c01f7f05f958d153969b9be54c..56b2abda5fb086d11ec0573d83d9319ab29d8c9c 100644 (file)
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -29,6 +29,7 @@
 #include "access/rewriteheap.h"
 #include "access/tableam.h"
 #include "access/tsmapi.h"
+#include "access/tuptoaster.h"
 #include "access/xact.h"
 #include "catalog/catalog.h"
 #include "catalog/index.h"
@@ -2009,6 +2010,57 @@ heapam_relation_size(Relation rel, ForkNumber forkNumber)
        return nblocks * BLCKSZ;
 }
 
+/*
+ * Check to see whether the table needs a TOAST table.  It does only if
+ * (1) there are any toastable attributes, and (2) the maximum length
+ * of a tuple could exceed TOAST_TUPLE_THRESHOLD.  (We don't want to
+ * create a toast table for something like "f1 varchar(20)".)
+ */
+static bool
+heapam_relation_needs_toast_table(Relation rel)
+{
+       int32           data_length = 0;
+       bool            maxlength_unknown = false;
+       bool            has_toastable_attrs = false;
+       TupleDesc       tupdesc = rel->rd_att;
+       int32           tuple_length;
+       int                     i;
+
+       for (i = 0; i < tupdesc->natts; i++)
+       {
+               Form_pg_attribute att = TupleDescAttr(tupdesc, i);
+
+               if (att->attisdropped)
+                       continue;
+               data_length = att_align_nominal(data_length, att->attalign);
+               if (att->attlen > 0)
+               {
+                       /* Fixed-length types are never toastable */
+                       data_length += att->attlen;
+               }
+               else
+               {
+                       int32           maxlen = type_maximum_size(att->atttypid,
+                                                                                                  att->atttypmod);
+
+                       if (maxlen < 0)
+                               maxlength_unknown = true;
+                       else
+                               data_length += maxlen;
+                       if (att->attstorage != 'p')
+                               has_toastable_attrs = true;
+               }
+       }
+       if (!has_toastable_attrs)
+               return false;                   /* nothing to toast? */
+       if (maxlength_unknown)
+               return true;                    /* any unlimited-length attrs? */
+       tuple_length = MAXALIGN(SizeofHeapTupleHeader +
+                                                       BITMAPLEN(tupdesc->natts)) +
+               MAXALIGN(data_length);
+       return (tuple_length > TOAST_TUPLE_THRESHOLD);
+}
+
 
 /* ------------------------------------------------------------------------
  * Planner related callbacks for the heap AM
@@ -2592,6 +2644,7 @@ static const TableAmRoutine heapam_methods = {
        .index_validate_scan = heapam_index_validate_scan,
 
        .relation_size = heapam_relation_size,
+       .relation_needs_toast_table = heapam_relation_needs_toast_table,
 
        .relation_estimate_size = heapam_estimate_rel_size,
 

diff --git a/src/backend/catalog/toasting.c b/src/backend/catalog/toasting.c
index 2276d3c5d36ce7db059ecea85142858b4a66a3d6..cf20ddb4e928e95974b61da6b2dc5900ae9bb927 100644 (file)
--- a/src/backend/catalog/toasting.c
+++ b/src/backend/catalog/toasting.c
@@ -15,7 +15,6 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
-#include "access/tuptoaster.h"
 #include "access/xact.h"
 #include "catalog/binary_upgrade.h"
 #include "catalog/catalog.h"
@@ -386,21 +385,11 @@ create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid,
 }
 
 /*
- * Check to see whether the table needs a TOAST table.  It does only if
- * (1) there are any toastable attributes, and (2) the maximum length
- * of a tuple could exceed TOAST_TUPLE_THRESHOLD.  (We don't want to
- * create a toast table for something like "f1 varchar(20)".)
+ * Check to see whether the table needs a TOAST table.
  */
 static bool
 needs_toast_table(Relation rel)
 {
-       int32           data_length = 0;
-       bool            maxlength_unknown = false;
-       bool            has_toastable_attrs = false;
-       TupleDesc       tupdesc;
-       int32           tuple_length;
-       int                     i;
-
        /*
         * No need to create a TOAST table for partitioned tables.
         */
@@ -423,39 +412,6 @@ needs_toast_table(Relation rel)
        if (IsCatalogRelation(rel) && !IsBootstrapProcessingMode())
                return false;
 
-       tupdesc = rel->rd_att;
-
-       for (i = 0; i < tupdesc->natts; i++)
-       {
-               Form_pg_attribute att = TupleDescAttr(tupdesc, i);
-
-               if (att->attisdropped)
-                       continue;
-               data_length = att_align_nominal(data_length, att->attalign);
-               if (att->attlen > 0)
-               {
-                       /* Fixed-length types are never toastable */
-                       data_length += att->attlen;
-               }
-               else
-               {
-                       int32           maxlen = type_maximum_size(att->atttypid,
-                                                                                                  att->atttypmod);
-
-                       if (maxlen < 0)
-                               maxlength_unknown = true;
-                       else
-                               data_length += maxlen;
-                       if (att->attstorage != 'p')
-                               has_toastable_attrs = true;
-               }
-       }
-       if (!has_toastable_attrs)
-               return false;                   /* nothing to toast? */
-       if (maxlength_unknown)
-               return true;                    /* any unlimited-length attrs? */
-       tuple_length = MAXALIGN(SizeofHeapTupleHeader +
-                                                       BITMAPLEN(tupdesc->natts)) +
-               MAXALIGN(data_length);
-       return (tuple_length > TOAST_TUPLE_THRESHOLD);
+       /* Otherwise, let the AM decide. */
+       return table_relation_needs_toast_table(rel);
 }

diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index 06eae2337a3bf031d185b60c32950f2ed2e16297..53b58c51da218cd98c7dea7281eb5862812ff7fb 100644 (file)
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -573,6 +573,16 @@ typedef struct TableAmRoutine
        uint64          (*relation_size) (Relation rel, ForkNumber forkNumber);
 
 
+       /*
+        * This callback should return true if the relation requires a TOAST table
+        * and false if it does not.  It may wish to examine the relation's
+        * tuple descriptor before making a decision, but if it uses some other
+        * method of storing large values (or if it does not support them) it can
+        * simply return false.
+        */
+       bool        (*relation_needs_toast_table) (Relation rel);
+
+
        /* ------------------------------------------------------------------------
         * Planner related functions.
         * ------------------------------------------------------------------------
@@ -1585,6 +1595,16 @@ table_relation_size(Relation rel, ForkNumber forkNumber)
        return rel->rd_tableam->relation_size(rel, forkNumber);
 }
 
+/*
+ * table_needs_toast_table - does this relation need a toast table?
+ */
+static inline bool
+table_relation_needs_toast_table(Relation rel)
+{
+       return rel->rd_tableam->relation_needs_toast_table(rel);
+}
+
+
 /* ----------------------------------------------------------------------------
  * Planner related functionality
  * ----------------------------------------------------------------------------