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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:46:48 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:46:48 +0000
commit311bcfc6b3acdd6fd152798c7f287ddf74fa2a98 (patch)
tree0ec307299b1dada3701e42f4ca6eda57d708261e /src/backend/access/table/toast_helper.c
parentInitial commit. (diff)
downloadpostgresql-15-upstream.tar.xz
postgresql-15-upstream.zip
Adding upstream version 15.4.upstream/15.4upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/backend/access/table/toast_helper.c')
-rw-r--r--src/backend/access/table/toast_helper.c337
1 files changed, 337 insertions, 0 deletions
diff --git a/src/backend/access/table/toast_helper.c b/src/backend/access/table/toast_helper.c
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+/*-------------------------------------------------------------------------
+ *
+ * toast_helper.c
+ * Helper functions for table AMs implementing compressed or
+ * out-of-line storage of varlena attributes.
+ *
+ * Copyright (c) 2000-2022, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ * src/backend/access/table/toast_helper.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/detoast.h"
+#include "access/table.h"
+#include "access/toast_helper.h"
+#include "access/toast_internals.h"
+#include "catalog/pg_type_d.h"
+
+
+/*
+ * Prepare to TOAST a tuple.
+ *
+ * tupleDesc, toast_values, and toast_isnull are required parameters; they
+ * provide the necessary details about the tuple to be toasted.
+ *
+ * toast_oldvalues and toast_oldisnull should be NULL for a newly-inserted
+ * tuple; for an update, they should describe the existing tuple.
+ *
+ * All of these arrays should have a length equal to tupleDesc->natts.
+ *
+ * On return, toast_flags and toast_attr will have been initialized.
+ * toast_flags is just a single uint8, but toast_attr is a caller-provided
+ * array with a length equal to tupleDesc->natts. The caller need not
+ * perform any initialization of the array before calling this function.
+ */
+void
+toast_tuple_init(ToastTupleContext *ttc)
+{
+ TupleDesc tupleDesc = ttc->ttc_rel->rd_att;
+ int numAttrs = tupleDesc->natts;
+ int i;
+
+ ttc->ttc_flags = 0;
+
+ for (i = 0; i < numAttrs; i++)
+ {
+ Form_pg_attribute att = TupleDescAttr(tupleDesc, i);
+ struct varlena *old_value;
+ struct varlena *new_value;
+
+ ttc->ttc_attr[i].tai_colflags = 0;
+ ttc->ttc_attr[i].tai_oldexternal = NULL;
+ ttc->ttc_attr[i].tai_compression = att->attcompression;
+
+ if (ttc->ttc_oldvalues != NULL)
+ {
+ /*
+ * For UPDATE get the old and new values of this attribute
+ */
+ old_value =
+ (struct varlena *) DatumGetPointer(ttc->ttc_oldvalues[i]);
+ new_value =
+ (struct varlena *) DatumGetPointer(ttc->ttc_values[i]);
+
+ /*
+ * If the old value is stored on disk, check if it has changed so
+ * we have to delete it later.
+ */
+ if (att->attlen == -1 && !ttc->ttc_oldisnull[i] &&
+ VARATT_IS_EXTERNAL_ONDISK(old_value))
+ {
+ if (ttc->ttc_isnull[i] ||
+ !VARATT_IS_EXTERNAL_ONDISK(new_value) ||
+ memcmp((char *) old_value, (char *) new_value,
+ VARSIZE_EXTERNAL(old_value)) != 0)
+ {
+ /*
+ * The old external stored value isn't needed any more
+ * after the update
+ */
+ ttc->ttc_attr[i].tai_colflags |= TOASTCOL_NEEDS_DELETE_OLD;
+ ttc->ttc_flags |= TOAST_NEEDS_DELETE_OLD;
+ }
+ else
+ {
+ /*
+ * This attribute isn't changed by this update so we reuse
+ * the original reference to the old value in the new
+ * tuple.
+ */
+ ttc->ttc_attr[i].tai_colflags |= TOASTCOL_IGNORE;
+ continue;
+ }
+ }
+ }
+ else
+ {
+ /*
+ * For INSERT simply get the new value
+ */
+ new_value = (struct varlena *) DatumGetPointer(ttc->ttc_values[i]);
+ }
+
+ /*
+ * Handle NULL attributes
+ */
+ if (ttc->ttc_isnull[i])
+ {
+ ttc->ttc_attr[i].tai_colflags |= TOASTCOL_IGNORE;
+ ttc->ttc_flags |= TOAST_HAS_NULLS;
+ continue;
+ }
+
+ /*
+ * Now look at varlena attributes
+ */
+ if (att->attlen == -1)
+ {
+ /*
+ * If the table's attribute says PLAIN always, force it so.
+ */
+ if (att->attstorage == TYPSTORAGE_PLAIN)
+ ttc->ttc_attr[i].tai_colflags |= TOASTCOL_IGNORE;
+
+ /*
+ * We took care of UPDATE above, so any external value we find
+ * still in the tuple must be someone else's that we cannot reuse
+ * (this includes the case of an out-of-line in-memory datum).
+ * Fetch it back (without decompression, unless we are forcing
+ * PLAIN storage). If necessary, we'll push it out as a new
+ * external value below.
+ */
+ if (VARATT_IS_EXTERNAL(new_value))
+ {
+ ttc->ttc_attr[i].tai_oldexternal = new_value;
+ if (att->attstorage == TYPSTORAGE_PLAIN)
+ new_value = detoast_attr(new_value);
+ else
+ new_value = detoast_external_attr(new_value);
+ ttc->ttc_values[i] = PointerGetDatum(new_value);
+ ttc->ttc_attr[i].tai_colflags |= TOASTCOL_NEEDS_FREE;
+ ttc->ttc_flags |= (TOAST_NEEDS_CHANGE | TOAST_NEEDS_FREE);
+ }
+
+ /*
+ * Remember the size of this attribute
+ */
+ ttc->ttc_attr[i].tai_size = VARSIZE_ANY(new_value);
+ }
+ else
+ {
+ /*
+ * Not a varlena attribute, plain storage always
+ */
+ ttc->ttc_attr[i].tai_colflags |= TOASTCOL_IGNORE;
+ }
+ }
+}
+
+/*
+ * Find the largest varlena attribute that satisfies certain criteria.
+ *
+ * The relevant column must not be marked TOASTCOL_IGNORE, and if the
+ * for_compression flag is passed as true, it must also not be marked
+ * TOASTCOL_INCOMPRESSIBLE.
+ *
+ * The column must have attstorage EXTERNAL or EXTENDED if check_main is
+ * false, and must have attstorage MAIN if check_main is true.
+ *
+ * The column must have a minimum size of MAXALIGN(TOAST_POINTER_SIZE);
+ * if not, no benefit is to be expected by compressing it.
+ *
+ * The return value is the index of the biggest suitable column, or
+ * -1 if there is none.
+ */
+int
+toast_tuple_find_biggest_attribute(ToastTupleContext *ttc,
+ bool for_compression, bool check_main)
+{
+ TupleDesc tupleDesc = ttc->ttc_rel->rd_att;
+ int numAttrs = tupleDesc->natts;
+ int biggest_attno = -1;
+ int32 biggest_size = MAXALIGN(TOAST_POINTER_SIZE);
+ int32 skip_colflags = TOASTCOL_IGNORE;
+ int i;
+
+ if (for_compression)
+ skip_colflags |= TOASTCOL_INCOMPRESSIBLE;
+
+ for (i = 0; i < numAttrs; i++)
+ {
+ Form_pg_attribute att = TupleDescAttr(tupleDesc, i);
+
+ if ((ttc->ttc_attr[i].tai_colflags & skip_colflags) != 0)
+ continue;
+ if (VARATT_IS_EXTERNAL(DatumGetPointer(ttc->ttc_values[i])))
+ continue; /* can't happen, toast_action would be PLAIN */
+ if (for_compression &&
+ VARATT_IS_COMPRESSED(DatumGetPointer(ttc->ttc_values[i])))
+ continue;
+ if (check_main && att->attstorage != TYPSTORAGE_MAIN)
+ continue;
+ if (!check_main && att->attstorage != TYPSTORAGE_EXTENDED &&
+ att->attstorage != TYPSTORAGE_EXTERNAL)
+ continue;
+
+ if (ttc->ttc_attr[i].tai_size > biggest_size)
+ {
+ biggest_attno = i;
+ biggest_size = ttc->ttc_attr[i].tai_size;
+ }
+ }
+
+ return biggest_attno;
+}
+
+/*
+ * Try compression for an attribute.
+ *
+ * If we find that the attribute is not compressible, mark it so.
+ */
+void
+toast_tuple_try_compression(ToastTupleContext *ttc, int attribute)
+{
+ Datum *value = &ttc->ttc_values[attribute];
+ Datum new_value;
+ ToastAttrInfo *attr = &ttc->ttc_attr[attribute];
+
+ new_value = toast_compress_datum(*value, attr->tai_compression);
+
+ if (DatumGetPointer(new_value) != NULL)
+ {
+ /* successful compression */
+ if ((attr->tai_colflags & TOASTCOL_NEEDS_FREE) != 0)
+ pfree(DatumGetPointer(*value));
+ *value = new_value;
+ attr->tai_colflags |= TOASTCOL_NEEDS_FREE;
+ attr->tai_size = VARSIZE(DatumGetPointer(*value));
+ ttc->ttc_flags |= (TOAST_NEEDS_CHANGE | TOAST_NEEDS_FREE);
+ }
+ else
+ {
+ /* incompressible, ignore on subsequent compression passes */
+ attr->tai_colflags |= TOASTCOL_INCOMPRESSIBLE;
+ }
+}
+
+/*
+ * Move an attribute to external storage.
+ */
+void
+toast_tuple_externalize(ToastTupleContext *ttc, int attribute, int options)
+{
+ Datum *value = &ttc->ttc_values[attribute];
+ Datum old_value = *value;
+ ToastAttrInfo *attr = &ttc->ttc_attr[attribute];
+
+ attr->tai_colflags |= TOASTCOL_IGNORE;
+ *value = toast_save_datum(ttc->ttc_rel, old_value, attr->tai_oldexternal,
+ options);
+ if ((attr->tai_colflags & TOASTCOL_NEEDS_FREE) != 0)
+ pfree(DatumGetPointer(old_value));
+ attr->tai_colflags |= TOASTCOL_NEEDS_FREE;
+ ttc->ttc_flags |= (TOAST_NEEDS_CHANGE | TOAST_NEEDS_FREE);
+}
+
+/*
+ * Perform appropriate cleanup after one tuple has been subjected to TOAST.
+ */
+void
+toast_tuple_cleanup(ToastTupleContext *ttc)
+{
+ TupleDesc tupleDesc = ttc->ttc_rel->rd_att;
+ int numAttrs = tupleDesc->natts;
+
+ /*
+ * Free allocated temp values
+ */
+ if ((ttc->ttc_flags & TOAST_NEEDS_FREE) != 0)
+ {
+ int i;
+
+ for (i = 0; i < numAttrs; i++)
+ {
+ ToastAttrInfo *attr = &ttc->ttc_attr[i];
+
+ if ((attr->tai_colflags & TOASTCOL_NEEDS_FREE) != 0)
+ pfree(DatumGetPointer(ttc->ttc_values[i]));
+ }
+ }
+
+ /*
+ * Delete external values from the old tuple
+ */
+ if ((ttc->ttc_flags & TOAST_NEEDS_DELETE_OLD) != 0)
+ {
+ int i;
+
+ for (i = 0; i < numAttrs; i++)
+ {
+ ToastAttrInfo *attr = &ttc->ttc_attr[i];
+
+ if ((attr->tai_colflags & TOASTCOL_NEEDS_DELETE_OLD) != 0)
+ toast_delete_datum(ttc->ttc_rel, ttc->ttc_oldvalues[i], false);
+ }
+ }
+}
+
+/*
+ * Check for external stored attributes and delete them from the secondary
+ * relation.
+ */
+void
+toast_delete_external(Relation rel, Datum *values, bool *isnull,
+ bool is_speculative)
+{
+ TupleDesc tupleDesc = rel->rd_att;
+ int numAttrs = tupleDesc->natts;
+ int i;
+
+ for (i = 0; i < numAttrs; i++)
+ {
+ if (TupleDescAttr(tupleDesc, i)->attlen == -1)
+ {
+ Datum value = values[i];
+
+ if (isnull[i])
+ continue;
+ else if (VARATT_IS_EXTERNAL_ONDISK(PointerGetDatum(value)))
+ toast_delete_datum(rel, value, is_speculative);
+ }
+ }
+}