From 401bc333397e96da5696ee2d74a905a0222348a0 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Tue, 19 Jun 2018 04:08:08 -0600
Subject: [PATCH 01/13] added function check_for_classic_model()

---
 libhdf5/hdf5file.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/libhdf5/hdf5file.c b/libhdf5/hdf5file.c
index 0bc1c337d3..ef27fafc95 100644
--- a/libhdf5/hdf5file.c
+++ b/libhdf5/hdf5file.c
@@ -2465,6 +2465,40 @@ nc4_rec_read_metadata(NC_GRP_INFO_T *grp)
    return retval;
 }
 
+/**
+ * @internal Check for the attribute that indicates that netcdf
+ * classic model is in use.
+ *
+ * @param root_grp pointer to the group info for the root group of the
+ * file.
+ *
+ * @return NC_NOERR No error.
+ * @author Ed Hartnett
+ */
+static int
+check_for_classic_model(NC_GRP_INFO_T *root_grp, int *is_classic)
+{
+   hid_t attid;
+
+   /* Check inputs. */
+   assert(!root_grp->parent && is_classic);
+
+   /* If this attribute exists in the root group, then classic model
+    * is in effect. */
+   if ((attid = H5Aopen_name(root_grp->hdf_grpid, NC3_STRICT_ATT_NAME)) < 0)
+   {
+      *is_classic = 0;
+   }
+   else
+   {
+      *is_classic = 1;
+      if (H5Aclose(attid) < 0)
+         return NC_EHDFERR;
+   }
+
+   return NC_NOERR;
+}
+
 /**
  * @internal Open a netcdf-4 file. Things have already been kicked off
  * in ncfunc.c in nc_open, but here the netCDF-4 part of opening a
@@ -2484,7 +2518,8 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
    hid_t fapl_id = H5P_DEFAULT;
    int retval;
    unsigned flags;
-   NC_HDF5_FILE_INFO_T* nc4_info = NULL;
+   NC_HDF5_FILE_INFO_T *nc4_info = NULL;
+   int is_classic;
 
 #ifdef USE_PARALLEL4
    NC_MPI_INFO* mpiinfo = NULL;
@@ -2605,6 +2640,12 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
    } else if ((nc4_info->hdfid = H5Fopen(path, flags, fapl_id)) < 0)
       BAIL(NC_EHDFERR);
 
+   /* Check for classic model attribute. */
+   if ((retval = check_for_classic_model(nc4_info->root_grp, &is_classic)))
+      BAIL(retval);
+   if (is_classic)
+      nc4_info->cmode |= NC_CLASSIC_MODEL;
+
    /* Now read in all the metadata. Some types and dimscale
     * information may be difficult to resolve here, if, for example, a
     * dataset of user-defined type is encountered before the

From 5f850408c303b5b04db9f64c4117aa02f1fc5a42 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Tue, 19 Jun 2018 04:40:00 -0600
Subject: [PATCH 02/13] adding lazy att handling

---
 include/nc4internal.h | 2 ++
 libhdf5/hdf5file.c    | 6 +++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/nc4internal.h b/include/nc4internal.h
index cc5e9feb83..75a56ef7fc 100644
--- a/include/nc4internal.h
+++ b/include/nc4internal.h
@@ -281,6 +281,7 @@ typedef struct NC_GRP_INFO
    hid_t hdf_grpid;
    struct NC_HDF5_FILE_INFO *nc4_info;
    struct NC_GRP_INFO *parent;
+   int atts_read;
    NCindex* children;		/* NCindex<struct NC_GRP_INFO*> */
    NCindex* dim;		/* NCindex<NC_DIM_INFO_T> * */
    NCindex* att;		/* NCindex<NC_ATT_INFO_T> * */
@@ -370,6 +371,7 @@ int nc4_rec_write_groups_types(NC_GRP_INFO_T *grp);
 int nc4_enddef_netcdf4_file(NC_HDF5_FILE_INFO_T *h5);
 int nc4_reopen_dataset(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var);
 int nc4_adjust_var_cache(NC_GRP_INFO_T *grp, NC_VAR_INFO_T * var);
+int nc4_read_grp_atts(NC_GRP_INFO_T *grp);
 
 /* The following functions manipulate the in-memory linked list of
    metadata, without using HDF calls. */
diff --git a/libhdf5/hdf5file.c b/libhdf5/hdf5file.c
index ef27fafc95..07ed88f88f 100644
--- a/libhdf5/hdf5file.c
+++ b/libhdf5/hdf5file.c
@@ -2083,8 +2083,8 @@ read_var(NC_GRP_INFO_T *grp, hid_t datasetid, const char *obj_name,
  * @return ::NC_EHDFERR HDF5 returned error.
  * @author Ed Hartnett
 */
-static int
-read_grp_atts(NC_GRP_INFO_T *grp)
+int
+nc4_read_grp_atts(NC_GRP_INFO_T *grp)
 {
    hid_t attid = -1;
    hsize_t num_obj, i;
@@ -2436,7 +2436,7 @@ nc4_rec_read_metadata(NC_GRP_INFO_T *grp)
    }
 
    /* Scan the group for global (i.e. group-level) attributes. */
-   if ((retval = read_grp_atts(grp)))
+   if ((retval = nc4_read_grp_atts(grp)))
       BAIL(retval);
 
    /* when exiting define mode, mark all variable written */

From dad70cf8809a68d6930d592a35ed9a41807f494c Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Tue, 19 Jun 2018 04:54:03 -0600
Subject: [PATCH 03/13] more lazy atts

---
 libhdf4/hdf4file.c | 1 +
 libhdf5/hdf5file.c | 3 +++
 libsrc4/nc4attr.c  | 6 ++++++
 3 files changed, 10 insertions(+)

diff --git a/libhdf4/hdf4file.c b/libhdf4/hdf4file.c
index f02794036b..4488efde3f 100644
--- a/libhdf4/hdf4file.c
+++ b/libhdf4/hdf4file.c
@@ -645,6 +645,7 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
    for (a = 0; a < num_gatts; a++)
       if ((retval = hdf4_read_att(h5, NULL, a)))
          break;
+   h5->root_grp->atts_read = 1;
 
    /* Read each dataset. */
    if (!retval)
diff --git a/libhdf5/hdf5file.c b/libhdf5/hdf5file.c
index 07ed88f88f..d78c45f02f 100644
--- a/libhdf5/hdf5file.c
+++ b/libhdf5/hdf5file.c
@@ -2138,6 +2138,9 @@ nc4_read_grp_atts(NC_GRP_INFO_T *grp)
       attid = -1;
    }
 
+   /* Remember that we have read the atts for this group. */
+   grp->atts_read = 1;
+
 exit:
    if (attid > 0) {
       if(H5Aclose(attid) < 0)
diff --git a/libsrc4/nc4attr.c b/libsrc4/nc4attr.c
index 39f23cc526..438e8011f9 100644
--- a/libsrc4/nc4attr.c
+++ b/libsrc4/nc4attr.c
@@ -150,6 +150,12 @@ nc4_get_att(int ncid, int varid, const char *name, nc_type *xtype,
    if ((retval = nc4_normalize_name(name, norm_name)))
       BAIL(retval);
 
+   /* Read the global atts for this group, if they have not been
+    * read. */
+   if (varid == NC_GLOBAL && !grp->atts_read)
+      if ((retval = nc4_read_grp_atts(grp)))
+         return retval;
+
    /* If this is one of the reserved atts, use nc_get_att_special. */
    if (nc->ext_ncid == ncid && varid == NC_GLOBAL) {
       const NC_reservedatt* ra = NC_findreserved(norm_name);

From 6b901692784f3b8dd62c70ed9eedc9aa674943df Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Tue, 19 Jun 2018 05:05:44 -0600
Subject: [PATCH 04/13] switching to att_not_read

---
 include/nc4internal.h | 2 +-
 libhdf4/hdf4file.c    | 1 -
 libhdf5/hdf5file.c    | 7 ++++++-
 libsrc4/nc4attr.c     | 2 +-
 4 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/nc4internal.h b/include/nc4internal.h
index 75a56ef7fc..97cee883e7 100644
--- a/include/nc4internal.h
+++ b/include/nc4internal.h
@@ -281,7 +281,7 @@ typedef struct NC_GRP_INFO
    hid_t hdf_grpid;
    struct NC_HDF5_FILE_INFO *nc4_info;
    struct NC_GRP_INFO *parent;
-   int atts_read;
+   int atts_not_read;
    NCindex* children;		/* NCindex<struct NC_GRP_INFO*> */
    NCindex* dim;		/* NCindex<NC_DIM_INFO_T> * */
    NCindex* att;		/* NCindex<NC_ATT_INFO_T> * */
diff --git a/libhdf4/hdf4file.c b/libhdf4/hdf4file.c
index 4488efde3f..f02794036b 100644
--- a/libhdf4/hdf4file.c
+++ b/libhdf4/hdf4file.c
@@ -645,7 +645,6 @@ NC_HDF4_open(const char *path, int mode, int basepe, size_t *chunksizehintp,
    for (a = 0; a < num_gatts; a++)
       if ((retval = hdf4_read_att(h5, NULL, a)))
          break;
-   h5->root_grp->atts_read = 1;
 
    /* Read each dataset. */
    if (!retval)
diff --git a/libhdf5/hdf5file.c b/libhdf5/hdf5file.c
index d78c45f02f..4d9d0e0db4 100644
--- a/libhdf5/hdf5file.c
+++ b/libhdf5/hdf5file.c
@@ -2139,7 +2139,7 @@ nc4_read_grp_atts(NC_GRP_INFO_T *grp)
    }
 
    /* Remember that we have read the atts for this group. */
-   grp->atts_read = 1;
+   grp->atts_not_read = 0;
 
 exit:
    if (attid > 0) {
@@ -3060,6 +3060,11 @@ NC4_inq(int ncid, int *ndimsp, int *nvarsp, int *nattsp, int *unlimdimidp)
    }
    if (nattsp)
    {
+      /* Do we need to read the atts? */
+      if (grp->atts_not_read)
+         if ((retval = nc4_read_grp_atts(grp)))
+            return retval;
+
       *nattsp = ncindexcount(grp->att);
    }
 
diff --git a/libsrc4/nc4attr.c b/libsrc4/nc4attr.c
index 438e8011f9..1d6704d841 100644
--- a/libsrc4/nc4attr.c
+++ b/libsrc4/nc4attr.c
@@ -152,7 +152,7 @@ nc4_get_att(int ncid, int varid, const char *name, nc_type *xtype,
 
    /* Read the global atts for this group, if they have not been
     * read. */
-   if (varid == NC_GLOBAL && !grp->atts_read)
+   if (varid == NC_GLOBAL && grp->atts_not_read)
       if ((retval = nc4_read_grp_atts(grp)))
          return retval;
 

From 2dc6676bd8b0d00c665dbbb55195b29c3a6d2285 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Tue, 19 Jun 2018 07:30:08 -0600
Subject: [PATCH 05/13] now checking for classic model

---
 libhdf5/hdf5file.c   | 27 ++++++++++-----------------
 nc_test4/tst_files.c |  1 +
 2 files changed, 11 insertions(+), 17 deletions(-)

diff --git a/libhdf5/hdf5file.c b/libhdf5/hdf5file.c
index 4d9d0e0db4..15f3a4e74b 100644
--- a/libhdf5/hdf5file.c
+++ b/libhdf5/hdf5file.c
@@ -2481,23 +2481,16 @@ nc4_rec_read_metadata(NC_GRP_INFO_T *grp)
 static int
 check_for_classic_model(NC_GRP_INFO_T *root_grp, int *is_classic)
 {
-   hid_t attid;
+   htri_t attr_exists = -1;
 
    /* Check inputs. */
    assert(!root_grp->parent && is_classic);
 
    /* If this attribute exists in the root group, then classic model
     * is in effect. */
-   if ((attid = H5Aopen_name(root_grp->hdf_grpid, NC3_STRICT_ATT_NAME)) < 0)
-   {
-      *is_classic = 0;
-   }
-   else
-   {
-      *is_classic = 1;
-      if (H5Aclose(attid) < 0)
-         return NC_EHDFERR;
-   }
+   if ((attr_exists = H5Aexists(root_grp->hdf_grpid, NC3_STRICT_ATT_NAME)) < 0)
+      return NC_EHDFERR;
+   *is_classic = attr_exists ? 1 : 0;
 
    return NC_NOERR;
 }
@@ -2643,12 +2636,6 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
    } else if ((nc4_info->hdfid = H5Fopen(path, flags, fapl_id)) < 0)
       BAIL(NC_EHDFERR);
 
-   /* Check for classic model attribute. */
-   if ((retval = check_for_classic_model(nc4_info->root_grp, &is_classic)))
-      BAIL(retval);
-   if (is_classic)
-      nc4_info->cmode |= NC_CLASSIC_MODEL;
-
    /* Now read in all the metadata. Some types and dimscale
     * information may be difficult to resolve here, if, for example, a
     * dataset of user-defined type is encountered before the
@@ -2656,6 +2643,12 @@ nc4_open_file(const char *path, int mode, void* parameters, NC *nc)
    if ((retval = nc4_rec_read_metadata(nc4_info->root_grp)))
       BAIL(retval);
 
+   /* Check for classic model attribute. */
+   if ((retval = check_for_classic_model(nc4_info->root_grp, &is_classic)))
+      BAIL(retval);
+   if (is_classic)
+      nc4_info->cmode |= NC_CLASSIC_MODEL;
+
    /* Now figure out which netCDF dims are indicated by the dimscale
     * information. */
    if ((retval = nc4_rec_match_dimscales(nc4_info->root_grp)))
diff --git a/nc_test4/tst_files.c b/nc_test4/tst_files.c
index 27e0021ba8..629ac14aef 100644
--- a/nc_test4/tst_files.c
+++ b/nc_test4/tst_files.c
@@ -82,6 +82,7 @@ main(int argc, char **argv)
       /* Check the contents. Then define a new variable. Since it's
        * netcdf-4, nc_enddef isn't required - it's called
        * automatically. */
+      hdf5_set_log_level(3);
       if (nc_open(FILE_NAME, NC_WRITE, &ncid)) ERR;
       if (nc_inq(ncid, &ndims, &nvars, &natts, &unlimdimid)) ERR;
       if (ndims != 2 || nvars != 2 || natts != 0 || unlimdimid != -1) ERR;

From 81add527f27aedd2589ce774dcfd2c9e2bd65a66 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Tue, 19 Jun 2018 07:39:42 -0600
Subject: [PATCH 06/13] lazy read of global atts now working

---
 libhdf5/hdf5attr.c    | 8 +++++++-
 libhdf5/hdf5file.c    | 5 +++--
 libsrc4/nc4internal.c | 8 ++++++++
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/libhdf5/hdf5attr.c b/libhdf5/hdf5attr.c
index 86ae0a61f0..1e0a6b5b04 100644
--- a/libhdf5/hdf5attr.c
+++ b/libhdf5/hdf5attr.c
@@ -175,9 +175,9 @@ NC4_del_att(int ncid, int varid, const char *name)
    NC_ATT_INFO_T *att;
    NCindex* attlist = NULL;
    hid_t locid = 0, datasetid = 0;
-   int retval = NC_NOERR;
    int i;
    size_t deletedid;
+   int retval;
 
    if (!name)
       return NC_EINVAL;
@@ -204,6 +204,12 @@ NC4_del_att(int ncid, int varid, const char *name)
          BAIL(retval);
    }
 
+   /* Do we need to read the atts? */
+   if (varid == NC_GLOBAL)
+      if (grp->atts_not_read)
+         if ((retval = nc4_read_grp_atts(grp)))
+            return retval;
+
    /* Get either the global or a variable attribute list. Also figure
       out the HDF5 location it's attached to. */
    attlist = getattlist(grp,varid,&var);
diff --git a/libhdf5/hdf5file.c b/libhdf5/hdf5file.c
index 15f3a4e74b..1fe400f53c 100644
--- a/libhdf5/hdf5file.c
+++ b/libhdf5/hdf5file.c
@@ -2439,8 +2439,9 @@ nc4_rec_read_metadata(NC_GRP_INFO_T *grp)
    }
 
    /* Scan the group for global (i.e. group-level) attributes. */
-   if ((retval = nc4_read_grp_atts(grp)))
-      BAIL(retval);
+   grp->atts_not_read = 1;
+   /* if ((retval = nc4_read_grp_atts(grp))) */
+   /*    BAIL(retval); */
 
    /* when exiting define mode, mark all variable written */
    for (i=0; i<ncindexsize(grp->vars); i++) {
diff --git a/libsrc4/nc4internal.c b/libsrc4/nc4internal.c
index 8f4409fc6d..3a18e35fbf 100644
--- a/libsrc4/nc4internal.c
+++ b/libsrc4/nc4internal.c
@@ -460,6 +460,7 @@ nc4_find_grp_att(NC_GRP_INFO_T *grp, int varid, const char *name, int attnum,
 {
    NC_VAR_INFO_T *var;
    NCindex* attlist = NULL;
+   int retval;
 
    assert(grp && grp->hdr.name);
    LOG((4, "nc4_find_grp_att: grp->name %s varid %d name %s attnum %d",
@@ -467,7 +468,14 @@ nc4_find_grp_att(NC_GRP_INFO_T *grp, int varid, const char *name, int attnum,
 
    /* Get either the global or a variable attribute list. */
    if (varid == NC_GLOBAL)
+   {
       attlist = grp->att;
+
+      /* Do we need to read the atts? */
+      if (grp->atts_not_read)
+         if ((retval = nc4_read_grp_atts(grp)))
+            return retval;
+   }
    else
    {
       var = (NC_VAR_INFO_T*)ncindexith(grp->vars,varid);

From a01da62481f80864c9c0110618e93e8e1977d639 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Tue, 19 Jun 2018 07:51:49 -0600
Subject: [PATCH 07/13] isolating code to read variable attributes

---
 include/nc4internal.h |  4 +---
 libhdf5/hdf5file.c    | 47 +++++++++++++++++++++++++++++++------------
 2 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/include/nc4internal.h b/include/nc4internal.h
index 97cee883e7..49dd2507a8 100644
--- a/include/nc4internal.h
+++ b/include/nc4internal.h
@@ -180,9 +180,7 @@ typedef struct NC_VAR_INFO
    nc_bool_t written_to;        /* True if variable has data written to it */
    struct NC_TYPE_INFO *type_info;
    hid_t hdf_datasetid;
-#if 0
-   int natts;			/* Use explicit index because there may be gaps in numbers */
-#endif
+   int atts_not_read;           /* If true, the atts have not yet been read. */
    NCindex* att; 		/* NCindex<NC_ATT_INFO_T*> */
    nc_bool_t no_fill;           /* True if no fill value is defined for var */
    void *fill_value;
diff --git a/libhdf5/hdf5file.c b/libhdf5/hdf5file.c
index 1fe400f53c..a32192a105 100644
--- a/libhdf5/hdf5file.c
+++ b/libhdf5/hdf5file.c
@@ -1800,6 +1800,36 @@ read_type(NC_GRP_INFO_T *grp, hid_t hdf_typeid, char *type_name)
    return retval;
 }
 
+/**
+ * @internal This function reads all the attributes of a variable.
+ *
+ * @param grp Pointer to the group info.
+ * @param var Pointer to the var info.
+ *
+ * @return NC_NOERR No error.
+ * @author Ed Hartnett
+ */
+int
+nc4_read_var_atts(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var)
+{
+   att_iter_info att_info;         /* Custom iteration information */
+
+   /* Check inputs. */
+   assert(grp && var);
+
+   /* Assign var and grp in struct. */
+   att_info.var = var;
+   att_info.grp = grp;
+
+   /* Now read all the attributes of this variable, ignoring the
+      ones that hold HDF5 dimension scale information. */
+   if ((H5Aiterate2(var->hdf_datasetid, H5_INDEX_CRT_ORDER, H5_ITER_INC, NULL,
+                    att_read_var_callbk, &att_info)) < 0)
+      return NC_EATTMETA;
+
+   return NC_NOERR;
+}
+
 /**
  * @internal This function is called by read_dataset(), (which is called
  * by nc4_rec_read_metadata()) when a netCDF variable is found in the
@@ -1825,7 +1855,6 @@ read_var(NC_GRP_INFO_T *grp, hid_t datasetid, const char *obj_name,
    hid_t access_pid = 0;
    int incr_id_rc = 0;          /* Whether the dataset ID's ref count has been incremented */
    int d;
-   att_iter_info att_info;         /* Custom iteration information */
    H5Z_filter_t filter;
    int num_filters;
    unsigned int cd_values_zip[CD_NELEMS_ZLIB];
@@ -2040,15 +2069,9 @@ read_var(NC_GRP_INFO_T *grp, hid_t datasetid, const char *obj_name,
       }
    }
 
-   /* Now read all the attributes of this variable, ignoring the
-      ones that hold HDF5 dimension scale information. */
-
-   att_info.var = var;
-   att_info.grp = grp;
-
-   if ((H5Aiterate2(var->hdf_datasetid, H5_INDEX_CRT_ORDER, H5_ITER_INC, NULL,
-                    att_read_var_callbk, &att_info)) < 0)
-      BAIL(NC_EATTMETA);
+   /* Read variable attributes. */
+   if ((retval = nc4_read_var_atts(grp, var)))
+      BAIL(retval);
 
    /* Is this a deflated variable with a chunksize greater than the
     * current cache size? */
@@ -2438,10 +2461,8 @@ nc4_rec_read_metadata(NC_GRP_INFO_T *grp)
          BAIL(NC_EHDFERR);
    }
 
-   /* Scan the group for global (i.e. group-level) attributes. */
+   /* Defer the reading of global atts until someone asks for one. */
    grp->atts_not_read = 1;
-   /* if ((retval = nc4_read_grp_atts(grp))) */
-   /*    BAIL(retval); */
 
    /* when exiting define mode, mark all variable written */
    for (i=0; i<ncindexsize(grp->vars); i++) {

From b524cd04bcef2bc0a5c06274121b55cd24c564e0 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Tue, 19 Jun 2018 07:56:54 -0600
Subject: [PATCH 08/13] adding calls to get var atts when needed

---
 include/nc4internal.h | 1 +
 libsrc4/nc4var.c      | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/include/nc4internal.h b/include/nc4internal.h
index 49dd2507a8..a16f27408a 100644
--- a/include/nc4internal.h
+++ b/include/nc4internal.h
@@ -370,6 +370,7 @@ int nc4_enddef_netcdf4_file(NC_HDF5_FILE_INFO_T *h5);
 int nc4_reopen_dataset(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var);
 int nc4_adjust_var_cache(NC_GRP_INFO_T *grp, NC_VAR_INFO_T * var);
 int nc4_read_grp_atts(NC_GRP_INFO_T *grp);
+int nc4_read_var_atts(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var);
 
 /* The following functions manipulate the in-memory linked list of
    metadata, without using HDF calls. */
diff --git a/libsrc4/nc4var.c b/libsrc4/nc4var.c
index ea0854c20f..81aeaa27df 100644
--- a/libsrc4/nc4var.c
+++ b/libsrc4/nc4var.c
@@ -752,6 +752,11 @@ NC4_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
    {
       if (nattsp)
       {
+         /* Do we need to read the atts? */
+         if (grp->atts_not_read)
+            if ((retval = nc4_read_grp_atts(grp)))
+               return retval;
+
 	 *nattsp = ncindexcount(grp->att);
       }
       return NC_NOERR;
@@ -775,6 +780,9 @@ NC4_inq_var_all(int ncid, int varid, char *name, nc_type *xtypep,
          dimidsp[d] = var->dimids[d];
    if (nattsp)
    {
+      if (var->atts_not_read)
+         if ((retval = nc4_read_var_atts(grp, var)))
+            return retval;
       *nattsp = ncindexcount(var->att);
    }
 

From 77936f2884392ae991cf761ef10c3834b6c1a31a Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Tue, 19 Jun 2018 08:25:19 -0600
Subject: [PATCH 09/13] more progress towards lazy read of atts for vars

---
 libhdf5/hdf5attr.c    | 84 ++++++++++++++++++++++++++++++++++---------
 libhdf5/hdf5file.c    |  3 ++
 libsrc4/nc4internal.c |  6 ++++
 3 files changed, 76 insertions(+), 17 deletions(-)

diff --git a/libhdf5/hdf5attr.c b/libhdf5/hdf5attr.c
index 1e0a6b5b04..e761dd910f 100644
--- a/libhdf5/hdf5attr.c
+++ b/libhdf5/hdf5attr.c
@@ -43,6 +43,54 @@ getattlist(NC_GRP_INFO_T *grp, int varid, NC_VAR_INFO_T **varp)
    }
 }
 
+/**
+ * @internal Get the attribute list for either a varid or NC_GLOBAL
+ *
+ * @param grp Group
+ * @param varid Variable ID | NC_BLOGAL
+ * @param varp Pointer that gets pointer to NC_VAR_INFO_T
+ * instance. Ignored if NULL.
+ * @param attlist Pointer that gets pointer to attribute list.
+ *
+ * @return NC_NOERR No error.
+ * @author Dennis Heimbigner, Ed Hartnett
+ */
+static int
+getattlist2(NC_GRP_INFO_T *grp, int varid, NC_VAR_INFO_T **varp,
+            NCindex **attlist)
+{
+   NC_VAR_INFO_T* var;
+   int retval;
+
+   if (varid == NC_GLOBAL)
+   {
+      /* Do we need to read the atts? */
+      if (grp->atts_not_read)
+         if ((retval = nc4_read_grp_atts(grp)))
+            return retval;
+
+      if (varp)
+         *varp = NULL;
+      *attlist = grp->att;
+   }
+   else
+   {
+      if (!(var = (NC_VAR_INFO_T *)ncindexith(grp->vars, varid)))
+         return NC_ENOTVAR;
+      assert(var->hdr.id == varid);
+
+      /* Do we need to read the atts? */
+      if (var->atts_not_read)
+         if ((retval = nc4_read_var_atts(grp, var)))
+            return retval;
+
+      if (varp)
+         *varp = var;
+      *attlist = var->att;
+   }
+   return NC_NOERR;
+}
+
 /**
  * @internal I think all atts should be named the exact same thing, to
  * avoid confusion!
@@ -92,11 +140,13 @@ NC4_rename_att(int ncid, int varid, const char *name, const char *newname)
    if ((retval = nc4_check_name(newname, norm_newname)))
       return retval;
 
-   /* Is new name in use? */
-   list = getattlist(grp,varid,&var);
-   if(list == NULL)
-      return NC_ENOTVAR;
+   /* Get the list of attributes. */
+   /* if (!(list = getattlist(grp,varid,&var))) */
+   /*    return NC_ENOTVAR; */
+   if ((retval = getattlist2(grp, varid, &var, &list)))
+      return retval;
 
+   /* Is new name in use? */
    att = (NC_ATT_INFO_T*)ncindexlookup(list,norm_newname);
    if(att != NULL)
       return NC_ENAMEINUSE;
@@ -204,17 +254,15 @@ NC4_del_att(int ncid, int varid, const char *name)
          BAIL(retval);
    }
 
-   /* Do we need to read the atts? */
-   if (varid == NC_GLOBAL)
-      if (grp->atts_not_read)
-         if ((retval = nc4_read_grp_atts(grp)))
-            return retval;
+   /* Get either the global or a variable attribute list. */
+   /* if (!(attlist = getattlist(grp,varid,NULL))) */
+   /*    return NC_ENOTVAR; */
+   if ((retval = getattlist2(grp, varid, &var, &attlist)))
+      return retval;
+   /* if (!(attlist = getattlist(grp,varid,NULL))) */
+   /*    return NC_ENOTVAR; */
 
-   /* Get either the global or a variable attribute list. Also figure
-      out the HDF5 location it's attached to. */
-   attlist = getattlist(grp,varid,&var);
-   if(attlist == NULL)
-      return NC_ENOTVAR;
+   /* Determine the location id in the HDF5 file. */
    if (varid == NC_GLOBAL)
       locid = grp->hdf_grpid;
    else if (var->created)
@@ -303,9 +351,11 @@ NC4_put_att(int ncid, int varid, const char *name, nc_type file_type,
 
    /* Find att, if it exists. (Must check varid first or nc_test will
     * break.) */
-   attlist = getattlist(grp,varid,&var);
-   if(attlist == NULL)
-      return NC_ENOTVAR;
+   if ((ret = getattlist2(grp, varid, &var, &attlist)))
+      return ret;
+   /* attlist = getattlist(grp,varid,&var); */
+   /* if(attlist == NULL) */
+   /*    return NC_ENOTVAR; */
 
    /* The length needs to be positive (cast needed for braindead
       systems with signed size_t). */
diff --git a/libhdf5/hdf5file.c b/libhdf5/hdf5file.c
index a32192a105..9b52090e51 100644
--- a/libhdf5/hdf5file.c
+++ b/libhdf5/hdf5file.c
@@ -1827,6 +1827,9 @@ nc4_read_var_atts(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var)
                     att_read_var_callbk, &att_info)) < 0)
       return NC_EATTMETA;
 
+   /* Remember that we have read the atts for this var. */
+   var->atts_not_read = 0;
+
    return NC_NOERR;
 }
 
diff --git a/libsrc4/nc4internal.c b/libsrc4/nc4internal.c
index 3a18e35fbf..87f9f51798 100644
--- a/libsrc4/nc4internal.c
+++ b/libsrc4/nc4internal.c
@@ -480,6 +480,12 @@ nc4_find_grp_att(NC_GRP_INFO_T *grp, int varid, const char *name, int attnum,
    {
       var = (NC_VAR_INFO_T*)ncindexith(grp->vars,varid);
       if (!var) return NC_ENOTVAR;
+
+      /* Do we need to read the var attributes? */
+      if (var->atts_not_read)
+         if ((retval = nc4_read_var_atts(grp, var)))
+            return retval;
+
       attlist = var->att;
       assert(var->hdr.id == varid);
    }

From eafe151f1317267410e4ed8ce0683bc565918ac4 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Tue, 19 Jun 2018 14:59:07 -0600
Subject: [PATCH 10/13] added test

---
 libhdf5/hdf5attr.c      |  38 ++---------
 libhdf5/hdf5file.c      |   7 +-
 libsrc4/nc4attr.c       |  25 +++++---
 nc_test4/Makefile.am    |   4 +-
 nc_test4/perftest.sh    |   6 +-
 nc_test4/tst_attsperf.c | 138 ++++++++++++++++++++++++++++++++++++++++
 6 files changed, 169 insertions(+), 49 deletions(-)
 mode change 100644 => 100755 nc_test4/perftest.sh
 create mode 100644 nc_test4/tst_attsperf.c

diff --git a/libhdf5/hdf5attr.c b/libhdf5/hdf5attr.c
index e761dd910f..264015d6b7 100644
--- a/libhdf5/hdf5attr.c
+++ b/libhdf5/hdf5attr.c
@@ -18,31 +18,6 @@
 
 int nc4typelen(nc_type type);
 
-/**
- * @internal Get the attribute list for either a varid or NC_GLOBAL
- *
- * @param grp Group
- * @param varid Variable ID | NC_BLOGAL
- * @param varp Pointer into which to return created NC_VAR_INFO_T instance
- *
- * @return Attribute list | NULL
- * @author Dennis Heimbigner
- */
-static NCindex *
-getattlist(NC_GRP_INFO_T *grp, int varid, NC_VAR_INFO_T **varp)
-{
-   if (varid == NC_GLOBAL) {
-      if(varp) *varp = NULL;
-      return grp->att;
-   } else {
-      NC_VAR_INFO_T* var = (NC_VAR_INFO_T*)ncindexith(grp->vars,varid);
-      if (!var) return NULL;
-      assert(var->hdr.id == varid);
-      if(varp) *varp = var;
-      return var->att;
-   }
-}
-
 /**
  * @internal Get the attribute list for either a varid or NC_GLOBAL
  *
@@ -56,7 +31,7 @@ getattlist(NC_GRP_INFO_T *grp, int varid, NC_VAR_INFO_T **varp)
  * @author Dennis Heimbigner, Ed Hartnett
  */
 static int
-getattlist2(NC_GRP_INFO_T *grp, int varid, NC_VAR_INFO_T **varp,
+getattlist(NC_GRP_INFO_T *grp, int varid, NC_VAR_INFO_T **varp,
             NCindex **attlist)
 {
    NC_VAR_INFO_T* var;
@@ -143,7 +118,7 @@ NC4_rename_att(int ncid, int varid, const char *name, const char *newname)
    /* Get the list of attributes. */
    /* if (!(list = getattlist(grp,varid,&var))) */
    /*    return NC_ENOTVAR; */
-   if ((retval = getattlist2(grp, varid, &var, &list)))
+   if ((retval = getattlist(grp, varid, &var, &list)))
       return retval;
 
    /* Is new name in use? */
@@ -257,10 +232,8 @@ NC4_del_att(int ncid, int varid, const char *name)
    /* Get either the global or a variable attribute list. */
    /* if (!(attlist = getattlist(grp,varid,NULL))) */
    /*    return NC_ENOTVAR; */
-   if ((retval = getattlist2(grp, varid, &var, &attlist)))
+   if ((retval = getattlist(grp, varid, &var, &attlist)))
       return retval;
-   /* if (!(attlist = getattlist(grp,varid,NULL))) */
-   /*    return NC_ENOTVAR; */
 
    /* Determine the location id in the HDF5 file. */
    if (varid == NC_GLOBAL)
@@ -351,11 +324,8 @@ NC4_put_att(int ncid, int varid, const char *name, nc_type file_type,
 
    /* Find att, if it exists. (Must check varid first or nc_test will
     * break.) */
-   if ((ret = getattlist2(grp, varid, &var, &attlist)))
+   if ((ret = getattlist(grp, varid, &var, &attlist)))
       return ret;
-   /* attlist = getattlist(grp,varid,&var); */
-   /* if(attlist == NULL) */
-   /*    return NC_ENOTVAR; */
 
    /* The length needs to be positive (cast needed for braindead
       systems with signed size_t). */
diff --git a/libhdf5/hdf5file.c b/libhdf5/hdf5file.c
index 9b52090e51..42962f878a 100644
--- a/libhdf5/hdf5file.c
+++ b/libhdf5/hdf5file.c
@@ -2073,8 +2073,9 @@ read_var(NC_GRP_INFO_T *grp, hid_t datasetid, const char *obj_name,
    }
 
    /* Read variable attributes. */
-   if ((retval = nc4_read_var_atts(grp, var)))
-      BAIL(retval);
+   var->atts_not_read = 1;
+   /* if ((retval = nc4_read_var_atts(grp, var))) */
+   /*    BAIL(retval); */
 
    /* Is this a deflated variable with a chunksize greater than the
     * current cache size? */
@@ -2466,6 +2467,8 @@ nc4_rec_read_metadata(NC_GRP_INFO_T *grp)
 
    /* Defer the reading of global atts until someone asks for one. */
    grp->atts_not_read = 1;
+   /* if ((retval = nc4_read_grp_atts(grp))) */
+   /*    return retval; */
 
    /* when exiting define mode, mark all variable written */
    for (i=0; i<ncindexsize(grp->vars); i++) {
diff --git a/libsrc4/nc4attr.c b/libsrc4/nc4attr.c
index 1d6704d841..1f69707203 100644
--- a/libsrc4/nc4attr.c
+++ b/libsrc4/nc4attr.c
@@ -116,6 +116,7 @@ nc4_get_att(int ncid, int varid, const char *name, nc_type *xtype,
    NC_GRP_INFO_T *grp;
    NC_HDF5_FILE_INFO_T *h5;
    NC_ATT_INFO_T *att = NULL;
+   NC_VAR_INFO_T *var;
    int my_attnum = -1;
    int need_to_convert = 0;
    int range_error = NC_NOERR;
@@ -136,9 +137,9 @@ nc4_get_att(int ncid, int varid, const char *name, nc_type *xtype,
       return retval;
 
    /* Check varid */
-   if (varid != NC_GLOBAL) {
-      NC_VAR_INFO_T* var = (NC_VAR_INFO_T*)ncindexith(grp->vars,varid);
-      if(var == NULL)
+   if (varid != NC_GLOBAL)
+   {
+      if (!(var = (NC_VAR_INFO_T*)ncindexith(grp->vars,varid)))
          return NC_ENOTVAR;
       assert(var->hdr.id == varid);
    }
@@ -150,11 +151,19 @@ nc4_get_att(int ncid, int varid, const char *name, nc_type *xtype,
    if ((retval = nc4_normalize_name(name, norm_name)))
       BAIL(retval);
 
-   /* Read the global atts for this group, if they have not been
-    * read. */
-   if (varid == NC_GLOBAL && grp->atts_not_read)
-      if ((retval = nc4_read_grp_atts(grp)))
-         return retval;
+   /* Read the atts for this group/var, if they have not been read. */
+   if (varid == NC_GLOBAL)
+   {
+      if (grp->atts_not_read)
+         if ((retval = nc4_read_grp_atts(grp)))
+            return retval;
+   }
+   else
+   {
+      if (var->atts_not_read)
+         if ((retval = nc4_read_var_atts(grp, var)))
+            return retval;
+   }
 
    /* If this is one of the reserved atts, use nc_get_att_special. */
    if (nc->ext_ncid == ncid && varid == NC_GLOBAL) {
diff --git a/nc_test4/Makefile.am b/nc_test4/Makefile.am
index f28637ab40..242a94658d 100644
--- a/nc_test4/Makefile.am
+++ b/nc_test4/Makefile.am
@@ -121,8 +121,8 @@ TESTS += run_par_test.sh
 endif
 
 if ENABLE_METADATA_PERF
-check_PROGRAMS += bigmeta openbigmeta
-TESTS += perftest.sh
+check_PROGRAMS += bigmeta openbigmeta tst_attsperf
+TESTS += tst_attsperf perftest.sh
 endif
 
 EXTRA_DIST = run_par_test.sh run_bm.sh run_bm_test1.sh			\
diff --git a/nc_test4/perftest.sh b/nc_test4/perftest.sh
old mode 100644
new mode 100755
index 04caa4900a..1facd9b575
--- a/nc_test4/perftest.sh
+++ b/nc_test4/perftest.sh
@@ -1,8 +1,8 @@
 #!/bin/sh
 
-#PROF=1
-#DEBUG=1
-#MEM=1
+PROF=1
+DEBUG=1
+MEM=1
 
 if test "x$srcdir" = x ; then srcdir=`pwd`; fi
 . ../test_common.sh
diff --git a/nc_test4/tst_attsperf.c b/nc_test4/tst_attsperf.c
new file mode 100644
index 0000000000..20f6b54cd6
--- /dev/null
+++ b/nc_test4/tst_attsperf.c
@@ -0,0 +1,138 @@
+/* This is part of the netCDF package. Copyright 2018 University
+ * Corporation for Atmospheric Research/Unidata. See COPYRIGHT file
+ * for conditions of use.
+ *
+ * Test the netCDF-4 attribute code.
+ *
+ * WARNING: do not attempt to run this under windows because of the use
+ * of gettimeofday().
+ *
+ * Ed Hartnett 6/19/18
+*/
+
+#include <config.h>
+#include <nc_tests.h>
+#include "err_macros.h"
+#include "nc4internal.h"
+#include <sys/time.h>
+
+#define TEST "tst_attsperf"
+#define VAR "bigvar"
+#define NDIMS 2
+#define DIM0 "d0"
+#define DIM1 "d1"
+#define DIMSIZE0 16
+#define DIMSIZE1 512
+#define TOTALSIZE (DIMSIZE0 * DIMSIZE1)
+#define NUM_ATTS 100
+#define ATT_LEN 10
+#define NUM_VARS 100
+
+int
+add_attributes(int ncid, int varid)
+{
+   char att_name[NC_MAX_NAME + 1];
+   double att_data[ATT_LEN];
+   int i, a;
+
+   /* Fill up data. */
+   for (i = 0; i < ATT_LEN; i++)
+      att_data[i] = i;
+
+   /* Write a bunch of attributes. */
+   for (a = 0; a < NUM_ATTS; a++)
+   {
+      sprintf(att_name, "%s_varid_%d_att_%d", TEST, varid, a);
+      if (nc_put_att_double(ncid, varid, att_name, NC_DOUBLE,
+                            ATT_LEN, att_data)) ERR;
+   }
+
+   return 0;
+}
+
+int
+buildfile(int file_no)
+{
+   int ncid, varid;
+   int dimids[NDIMS];
+   char file_name[NC_MAX_NAME + 1];
+   int v;
+
+   sprintf(file_name, "%s_%d.nc", TEST, file_no);
+
+   if (nc_create(file_name, NC_NETCDF4, &ncid)) ERR;
+
+   if (nc_def_dim(ncid, DIM0, DIMSIZE0, &dimids[0])) ERR;
+   if (nc_def_dim(ncid, DIM1, DIMSIZE1, &dimids[1])) ERR;
+   for (v = 0; v < NUM_VARS; v++)
+   {
+      char var_name[NC_MAX_NAME + 1];
+      sprintf(var_name, "%s_var_%d", TEST, v);
+      if (nc_def_var(ncid, var_name, NC_INT, NDIMS, dimids, &varid)) ERR;
+      if (add_attributes(ncid, v)) ERR;
+   }
+   if (add_attributes(ncid, NC_GLOBAL)) ERR;
+   if (nc_enddef(ncid)) ERR;
+
+   if (nc_close(ncid)) ERR;
+   return 0;
+}
+
+long long
+readfile(int inq_all)
+{
+   int ncid;
+   struct timeval starttime, endtime;
+   long long delta;
+   long long startt, endt;
+   char file_name[NC_MAX_NAME + 1];
+
+   sprintf(file_name, "%s_%d.nc", TEST, inq_all);
+
+   /* Start the clock. */
+   gettimeofday(&starttime, NULL);
+
+   /* Open the file. */
+   if (nc_open(file_name, NC_NETCDF4, &ncid)) ERR;
+
+   /* Simulate old open by triggering attribute reads, if desired. */
+   if (inq_all)
+   {
+      int natts;
+      int v;
+
+      /* When checking the number of atts, we trigger the read. */
+      if (nc_inq(ncid, NULL, NULL, &natts, NULL)) ERR;
+      for (v = 0; v < NUM_VARS; v++)
+         if (nc_inq_varnatts(ncid, v, &natts)) ERR;
+   }
+   gettimeofday(&endtime, NULL);
+
+   /* Close the file. */
+   if (nc_close(ncid)) ERR;
+
+   /* Compute the time delta */
+   startt = (1000000 * starttime.tv_sec) + starttime.tv_usec;
+   endt = (1000000 * endtime.tv_sec) + endtime.tv_usec;
+   delta = endt - startt;
+   return delta;
+}
+
+int
+main(int argc, char **argv)
+{
+   long long zerodelta, onedelta, factor;
+
+   printf("testing speed of open with files with lots of metadata...\n");
+   if (buildfile(0)) ERR;
+   if (buildfile(1)) ERR;
+   if ((zerodelta = readfile(0)) == -1) ERR;
+   if ((onedelta = readfile(1)) == -1) ERR;
+
+   /* Print results to the millisec */
+   factor = onedelta / zerodelta;
+   printf("Lazy Atts time=%lld Read Atts at Open time=%lld Speedup=%lld\n",
+          zerodelta, onedelta, factor);
+   SUMMARIZE_ERR;
+   FINAL_RESULTS;
+}

From d5baca7f978ccf7e2599cb04f67053c250290692 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Thu, 21 Jun 2018 06:36:12 -0600
Subject: [PATCH 11/13] fixed test issue

---
 nc_test4/perftest.sh | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/nc_test4/perftest.sh b/nc_test4/perftest.sh
index 1facd9b575..04caa4900a 100755
--- a/nc_test4/perftest.sh
+++ b/nc_test4/perftest.sh
@@ -1,8 +1,8 @@
 #!/bin/sh
 
-PROF=1
-DEBUG=1
-MEM=1
+#PROF=1
+#DEBUG=1
+#MEM=1
 
 if test "x$srcdir" = x ; then srcdir=`pwd`; fi
 . ../test_common.sh

From 97faffe0721e6746489ed58abecaac9b13ac10a9 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Thu, 21 Jun 2018 06:51:45 -0600
Subject: [PATCH 12/13] fixed test issue

---
 nc_test4/tst_files.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/nc_test4/tst_files.c b/nc_test4/tst_files.c
index 629ac14aef..27e0021ba8 100644
--- a/nc_test4/tst_files.c
+++ b/nc_test4/tst_files.c
@@ -82,7 +82,6 @@ main(int argc, char **argv)
       /* Check the contents. Then define a new variable. Since it's
        * netcdf-4, nc_enddef isn't required - it's called
        * automatically. */
-      hdf5_set_log_level(3);
       if (nc_open(FILE_NAME, NC_WRITE, &ncid)) ERR;
       if (nc_inq(ncid, &ndims, &nvars, &natts, &unlimdimid)) ERR;
       if (ndims != 2 || nvars != 2 || natts != 0 || unlimdimid != -1) ERR;

From d4967405b407e0a8e564cdf94ea83c785609f7a0 Mon Sep 17 00:00:00 2001
From: Ed Hartnett <edwardjameshartnett@gmail.com>
Date: Thu, 21 Jun 2018 19:49:30 -0600
Subject: [PATCH 13/13] cleaned up

---
 libhdf5/hdf5attr.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/libhdf5/hdf5attr.c b/libhdf5/hdf5attr.c
index 264015d6b7..bc876f3894 100644
--- a/libhdf5/hdf5attr.c
+++ b/libhdf5/hdf5attr.c
@@ -116,8 +116,6 @@ NC4_rename_att(int ncid, int varid, const char *name, const char *newname)
       return retval;
 
    /* Get the list of attributes. */
-   /* if (!(list = getattlist(grp,varid,&var))) */
-   /*    return NC_ENOTVAR; */
    if ((retval = getattlist(grp, varid, &var, &list)))
       return retval;
 
@@ -230,8 +228,6 @@ NC4_del_att(int ncid, int varid, const char *name)
    }
 
    /* Get either the global or a variable attribute list. */
-   /* if (!(attlist = getattlist(grp,varid,NULL))) */
-   /*    return NC_ENOTVAR; */
    if ((retval = getattlist(grp, varid, &var, &attlist)))
       return retval;